Resist composition, method of forming resist pattern and polymeric compound

ABSTRACT

A resist composition including a base component (A) which exhibits changed solubility in a developing solution under action of acid and an acid-generator component (B) which generates acid upon exposure, the base component (A) containing a polymeric compound (A1) having a structural unit (a5) represented by general formula (a5-0) shown below (R 1  represents a sulfur atom or an oxygen atom; R 2  represents a single bond or a divalent linking group; and Y represents an aromatic hydrocarbon group or an aliphatic hydrocarbon group having a polycyclic group, provided that the aromatic hydrocarbon group or the aliphatic hydrocarbon may have a carbon atom or a hydrogen atom thereof substituted with a substituent.

TECHNICAL FIELD

The present invention relates to a novel compound, a polymeric compoundincluding a structural unit derived from the compound, a resistcomposition including the polymeric compound, and a method of forming aresist pattern using the resist composition.

Priority is claimed on Japanese Patent Application No. 2011-245904,filed Nov. 9, 2011, the content of which is incorporated herein byreference.

BACKGROUND ART

In lithography techniques, for example, a resist film composed of aresist material is formed on a substrate, and the resist film issubjected to selective exposure of radial rays such as light or electronbeam through a mask having a predetermined pattern, followed bydevelopment, thereby forming a resist pattern having a predeterminedshape on the resist film.

A resist material in which the exposed portions become soluble in adeveloping solution is called a positive-type, and a resist material inwhich the exposed portions become insoluble in a developing solution iscalled a negative-type.

In recent years, in the production of semiconductor elements and liquidcrystal display elements, advances in lithography techniques have leadto rapid progress in the field of pattern miniaturization.

Typically, these miniaturization techniques involve shortening thewavelength (increasing the energy) of the exposure light source.Conventionally, ultraviolet radiation typified by g-line and i-lineradiation has been used, but nowadays KrF excimer lasers and ArF excimerlasers are starting to be introduced in mass production. Furthermore,research is also being conducted into lithography techniques that use anexposure light source having a wavelength shorter (energy higher) thanthese excimer lasers, such as electron beam, extreme ultravioletradiation (EUV), and X ray.

Resist materials for use with these types of exposure light sourcesrequire lithography properties such as a high resolution capable ofreproducing patterns of minute dimensions, and a high level ofsensitivity to these types of exposure light sources.

As a resist material that satisfies these conditions, a chemicallyamplified composition is used, which includes a base material componentthat exhibits a changed solubility in a developing solution under theaction of acid and an acid-generator component that generates acid uponexposure.

For example, in the case where the developing solution is an alkalideveloping solution (alkali developing process), a chemically amplifiedpositive resist which contains, as a base component (base resin), aresin which exhibits increased solubility in an alkali developingsolution under action of acid, and an acid generator is typically used.If the resist film formed using the resist composition is selectivelyexposed during formation of a resist pattern, then within the exposedportions, acid is generated from the acid-generator component, and theaction of this acid causes an increase in the solubility of the resincomponent in an alkali developing solution, making the exposed portionssoluble in the alkali developing solution. In this manner, the unexposedportions remain to form a positive resist pattern. The base resin usedexhibits increased polarity by the action of acid, thereby exhibitingincreased solubility in an alkali developing solution, whereas thesolubility in an organic solvent is decreased. When such a base resin isapplied to a process using a developing solution containing an organicsolvent (organic developing solution) (hereafter, this process isreferred to as “solvent developing process” or “negative tone-developingprocess”) instead of an alkali developing process, the solubility of theexposed portions in an organic developing solution is decreased.Therefore, in a solvent developing process, the unexposed portions ofthe resist film are dissolved and removed by an organic solvent-typedeveloping solution to thereby form a negative-tone resist pattern inwhich the exposed portions remain. For example, Patent Document 1proposes a negative tone-developing process and a resist compositionused for the process.

Currently, resins that contain structural units derived from(meth)acrylate esters within the main chain (acrylic resins) are nowwidely used as base resins for resist compositions that use ArF excimerlaser lithography, as they exhibit excellent transparency in thevicinity of 193 nm (for example, see Patent Document 2).

In general, the base resin contains a plurality of structural units forimproving lithography properties and the like. For example, in the caseof a resin component which exhibits increased polarity by the action ofacid, a base resin containing a plurality of structural units such as astructural unit having an acid decomposable group that is decomposed bythe action of acid generated from the acid generator component, astructural unit having a polar group such as a hydroxyl group, astructural unit having a lactone structure, and the like is typicallyused. In particular, structural units having a polar group are widelyused as they enhance the affinity for an alkali developing solution, andcontributes to improvement in resolution.

Recently, a base resin having a structural unit containing an imidegroup has been proposed (see Patent Document 3). It is presumed thatsuch as base resin contributes to improvement in resolution and maskreproducibility.

DOCUMENTS OF RELATED ART Patent Document

-   [Patent Document 1] Japanese Unexamined Patent Application, First    Publication No. 2009-025723-   [Patent Document 2] Japanese Unexamined Patent Application, First    Publication No. 2003-241385-   [Patent Document 3] Japanese Unexamined Patent Application, First    Publication No. 2006-063318

SUMMARY OF THE INVENTION

As further progress is made in lithography techniques and theapplication field for lithography techniques is expected to expand,development of a novel material for use in lithography will be desired.

For example, as miniaturization of resist patterns progress, furtherimprovement will be demanded for resist materials with respect tovarious lithography properties such as resolution, roughness (LWR (linewidth roughness: non-uniformity of the line width) and the like in thecase of a line pattern, and circularity in the case of a hole pattern),and exposure latitude, as well as high sensitivity.

In addition, as progress is made in lithography techniques(miniaturization), downsizing of the thickness of the resist film isproceeding. Thus, improvement in etching resistance is also demandedwhen etching is conducted using the pattern portion as a mask.

The present invention takes the above circumstances into consideration,with an object of providing a resist composition which exhibitsexcellent sensitivity, resolution, lithography properties and etchingresistance, a compound useful for the resist composition, and a methodof forming a resist pattern using the resist composition.

For solving the above-mentioned problems, the present invention employsthe following aspects.

Specifically, a first aspect of the present invention is a resistcomposition including a base component (A) which exhibits changedsolubility in a developing solution under action of acid and anacid-generator component (B) which generates acid upon exposure, thebase component (A) containing a polymeric compound (A1) having astructural unit (a5) represented by general formula (a5-0) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R¹represents a sulfur atom or an oxygen atom; R² represents a single bondor a divalent linking group; and Y represents an aromatic hydrocarbongroup or an aliphatic hydrocarbon group having a polycyclic group,provided that the aromatic hydrocarbon group or the aliphatichydrocarbon may have a carbon atom or a hydrogen atom thereofsubstituted with a substituent.

A second aspect of the present invention is a method of forming a resistpattern, including: using a resist composition according to the firstaspect to form a resist film on a substrate, subjecting the resist filmto exposure, and subjecting the resist film to developing to form aresist pattern.

A third aspect of the present invention is a compound represented bygeneral formula (1) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R¹represents a sulfur atom or an oxygen atom; R² represents a single bondor a divalent linking group; and Y represents an aromatic hydrocarbongroup or an aliphatic hydrocarbon group having a polycyclic group,provided that the aromatic hydrocarbon group or the aliphatichydrocarbon may have a carbon atom or a hydrogen atom thereofsubstituted with a substituent.

A fourth aspect of the present invention is a polymeric compound havinga structural unit (a5) represented by general formula (a5-0) shownbelow.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R¹represents a sulfur atom or an oxygen atom; R² represents a single bondor a divalent linking group; and Y represents an aromatic hydrocarbongroup or an aliphatic hydrocarbon group having a polycyclic group,provided that the aromatic hydrocarbon group or the aliphatichydrocarbon may have a carbon atom or a hydrogen atom thereofsubstituted with a substituent.

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified. The same applies forthe alkyl group within an alkoxy group.

The term “alkylene group” includes linear, branched or cyclic, divalentsaturated hydrocarbon, unless otherwise specified.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group is substituted with a halogen atom, anda “halogenated alkylene group” is a group in which part or all of thehydrogen atoms of an alkylene group is substituted with a halogen atom.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

A “fluorinated alkyl group” is a group in which part or all of thehydrogen atoms within an alkyl group have been substituted with afluorine atom. A “fluorinated alkylene group” is a group in which partor all of the hydrogen atoms within an alkylene group have beensubstituted with a fluorine atom.

A “hydroxyalkyl group” is a group in which part or all of the hydrogenatoms within an alkyl group have been substituted with a hydroxyl group.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (resin, polymer, copolymer).

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

According to the present invention, there are provided a resistcomposition which exhibits excellent sensitivity, resolution,lithography properties and etching resistance, a compound useful for theresist composition, a polymeric compound having a structural unitderived from the compound, and a method of forming a resist patternusing the resist composition.

MODE FOR CARRYING OUT THE INVENTION

<<Resist Composition>>

The resist composition of the present invention includes a basecomponent (A) (hereafter, referred to as “component (A)”) which exhibitschanged solubility in a developing solution under action of acid, and anacid-generator component (B) (hereafter, referred to as “component (B)”)which generates acid upon exposure.

When a resist film is formed using the resist composition and the formedresist film is subjected to a selective exposure, acid is generated fromthe component (B) at exposed portions, and the generated acid acts onthe component (A) to change the solubility of the component (A) in adeveloping solution, whereas the solubility of the component (A) in adeveloping solution is not changed at unexposed portions, therebygenerating difference in solubility in a developing solution betweenexposed portions and unexposed portions. Therefore, by subjecting theresist film to development, the exposed portions are dissolved andremoved to form a positive-tone resist pattern in the case of a positiveresist, whereas the unexposed portions are dissolved and removed to forma negative-tone resist pattern in the case of a negative resist.

In the present specification, a resist composition which forms apositive resist pattern by dissolving and removing the exposed portionsis called a positive resist composition, and a resist composition whichforms a negative resist pattern by dissolving and removing the unexposedportions is called a negative resist composition.

The resist composition of the present invention may be either a positiveresist composition or a negative resist composition.

Further, in the formation of a resist pattern, the resist composition ofthe present invention can be applied to an alkali developing processusing an alkali developing solution in the developing treatment, or asolvent developing process using a developing solution containing anorganic solvent (organic developing solution) in the developingtreatment.

<Component (A)>

The component (A) used in the resist composition of the presentinvention includes a polymeric compound (A1) (hereafter, referred to as“component (A1)”) including a structural unit (a5) represented bygeneral formula (a5-0).

Here, the term “base component” refers to an organic compound capable offorming a film, and is preferably an organic compound having a molecularweight of 500 or more. When the organic compound has a molecular weightof 500 or more, the film-forming ability is improved, and a resistpattern of nano level can be easily formed.

The organic compound used as the base component is broadly classifiedinto non-polymers and polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereafter, a “lowmolecular weight compound” refers to a non-polymer having a molecularweight in the range of 500 to less than 4,000.

As a polymer, any of those which have a molecular weight of 1,000 ormore is generally used. Hereafter, a “polymeric compound” or a “resin”refers to a polymer having a molecular weight of 1,000 or more.

As the molecular weight of the polymer, the weight average molecularweight in terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC) is used.

[Component (A1)]

The component (A1) may be a resin that exhibits increased solubility ina developing solution under action of acid or a resin that exhibitsdecreased solubility in a developing solution under action of acid.

When the resist composition of the present invention is a resistcomposition that forms a negative-tone resist pattern in an alkalideveloping process (or a positive-tone resist pattern in a solventdeveloping process), as the component (A1), a polymeric compound that issoluble in an alkali developing solution (hereafter, this polymericcompound is sometimes referred to as “component (A1-2)”) is preferablyused, and a cross-linking component is further added.

The component (A1-2) generally has an alkali-soluble group such as ahydroxy group, a carboxy group or an amino group. The cross-linkingcomponent used has a reactive group such as a methylol group or analkoxymethyl group that reacts with the alkali-soluble group by theaction of acid. When a resist film is formed using the resistcomposition and the formed resist film is subjected to a selectiveexposure, acid is generated from the component (B) at exposed portions,and the action of acid causes cross-linking between the component (A1-2)and the cross-linking component, thereby decreasing the number ofalkali-soluble groups of the component (A1-2) and the polarity, andincreasing the molecular weight. As a result, solubility in an alkalideveloping solution is decreased (solubility in an organic developingsolution is increased). Therefore, in the formation of a resist pattern,by conducting selective exposure of a resist film formed by applying theresist composition to a substrate, the exposed portions become insolublein an alkali developing solution (soluble in an organic developingsolution), whereas the unexposed portions remain soluble in an alkalideveloping solution (insoluble in an organic developing solution), andhence, a negative resist pattern can be formed by conducting developmentusing an alkali developing solution. On the other hand, when an organicdeveloping solution is used as the developing solution, a positiveresist pattern can be formed.

As the cross-linking agent, typically, an amino-based cross-linkingagent such as a glycoluril having a methylol group or alkoxymethylgroup, or a melamine-based cross-linking agent is preferable, as itenables formation of a resist pattern with minimal swelling. The amountof the cross-linker added is preferably within a range from 1 to 50parts by weight, relative to 100 parts by weight of the alkali-solubleresin.

When component (A1-2) is self-crosslinkable (e.g., when the component(A1-2) has a group that reacts with an alkali-soluble group by theaction of acid), the cross-linking component does not necessarily beadded.

When the resist composition of the present invention is a resistcomposition that forms a positive-tone resist pattern in an alkalideveloping process (or a negative-tone resist pattern in a solventdeveloping process), as the component (A1), a polymeric compound thatexhibits increased polarity by the action of acid (hereafter, thispolymeric compound is sometimes referred to as “(A1-1)”) is preferablyused. Since the polarity of the component (A1-1) is changed prior to andafter exposure, by using the component (A1-1), an excellent developmentcontrast can be achieved not only in an alkali developing process, butalso in a solvent developing process.

More specifically, in the case of applying an alkali developing process,the component (A1-1) is substantially insoluble in an alkali developingsolution prior to exposure, but when acid is generated from thecomponent (B) upon exposure, the action of this acid causes an increasein the polarity of the base component, thereby increasing the solubilityof the component (A1-1) in an alkali developing solution. Therefore, inthe formation of a resist pattern, by conducting selective exposure of aresist film formed by applying the resist composition to a substrate,the exposed portions change from an insoluble state to a soluble statein an alkali developing solution, whereas the unexposed portions remaininsoluble in an alkali developing solution, and hence, contrast can beobtained between the exposed portions and the unexposed portions, and apositive resist pattern can be formed by alkali developing. On the otherhand, in the case of a solvent developing process, the component (A1-1)exhibits high solubility in an organic developing solution prior toexposure, and when acid is generated from the component (B) uponexposure, the polarity of the component (A-1) is increased by the actionof the generated acid, thereby decreasing the solubility of thecomponent (A1-1) in an organic developing solution. Therefore, in theformation of a resist pattern, by conducting selective exposure of aresist film formed by applying the resist composition to a substrate,the exposed portions changes from an soluble state to an insoluble statein an organic developing solution, whereas the unexposed portions remainsoluble in an organic developing solution. As a result, by conductingdevelopment using an organic developing solution, a contrast can be madebetween the exposed portions and unexposed portions, thereby enablingthe formation of a negative resist pattern.

Among these, as the component (A1), the component (A1-1) is preferable.That is, the resist composition of the present invention is preferably achemically amplified resist composition which becomes a positive type inthe case of an alkali developing process, and a negative type in thecase of a solvent developing process.

As the component (A1-1), it is particularly desirable to include, inaddition to the structural unit (a5), a structural unit (a1) containingan acid decomposable group that exhibits increased polarity by theaction of acid. As the structural unit (a1), a structural unit derivedfrom an acrylate ester which may have the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent ispreferable.

The component (A1-1) preferably includes, in addition to the structuralunit (a5) and the structural unit (a1), a structural unit (a2)containing a —SO₂— containing cyclic group or a lactone-containingcyclic group.

Further, the component (A1-1) preferably includes, in addition to thestructural unit (a5) and the structural unit (a1), or in addition to thestructural unit (a5), the structural unit (a1) and the structural unit(a2), a structural unit (a3) containing a polar group.

Structural Unit (a5)

The structural unit (a5) is a structural unit represented by generalformula (a5-0) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R¹represents a sulfur atom or an oxygen atom; R² represents a single bondor a divalent linking group; and Y represents an aromatic hydrocarbongroup or an aliphatic hydrocarbon group having a polycyclic group,provided that the aromatic hydrocarbon group or the aliphatichydrocarbon may have a carbon atom or a hydrogen atom thereofsubstituted with a substituent.

In formula (a5-0), R represents a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms.

Examples of the alkyl group of 1 to 5 carbon atoms for R include linearor branched alkyl groups such as a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group and a neopentylgroup.

Examples of the halogenated alkyl group of 1 to 5 carbon atoms for Rinclude groups in which part or all of the hydrogen atoms of theaforementioned alkyl groups of 1 to 5 carbon atoms have been substitutedwith halogen atoms. Examples of the halogen atom include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is particularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, a hydrogenatom or an alkyl group of 1 to 5 carbon atoms is more preferable, and ahydrogen atom or a methyl group is particularly desirable.

In formula (a5-0), R¹ represents a sulfur atom or an oxygen atom, and anoxygen atom is preferable.

In the formula (a5-0), R² represents a single bond or a divalent linkinggroup.

The divalent linking group for R² is not particularly limited, andpreferable examples thereof include a divalent hydrocarbon group whichmay have a substituent and a divalent linking group containing a heteroatom.

(Divalent Hydrocarbon Group which May have a Substituent)

A hydrocarbon “has a substituent” means that part or all of the hydrogenatoms within the hydrocarbon group is substituted with a substituent (agroup or an atom other than hydrogen).

The hydrocarbon group may be either an aliphatic hydrocarbon group or anaromatic hydrocarbon group. An “aliphatic hydrocarbon group” refers to ahydrocarbon group that has no aromaticity.

The divalent aliphatic hydrocarbon group as the divalent hydrocarbongroup for R² may be either saturated or unsaturated. In general, thedivalent aliphatic hydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

The linear or branched aliphatic hydrocarbon group preferably has 1 to10 carbon atoms, more preferably 1 to 6, still more preferably 1 to 4,and most preferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated alkyl group of 1 to 5 carbon atoms, and an oxygen atom (═O).

As examples of the hydrocarbon group containing a ring in the structurethereof, an alicyclic hydrocarbon group (a group in which two hydrogenatoms have been removed from an aliphatic hydrocarbon ring), a group inwhich the alicyclic hydrocarbon group is bonded to the terminal of theaforementioned chain-like aliphatic hydrocarbon group, and a group inwhich the alicyclic group is interposed within the aforementioned linearor branched aliphatic hydrocarbon group, can be given. As the linear orbranched aliphatic hydrocarbon group, the same groups as those describedabove can be used.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a monocyclic group or apolycyclic group. As the monocyclic aliphatic hydrocarbon group, a groupin which 2 hydrogen atoms have been removed from a monocycloalkane ispreferable. The monocycloalkane preferably has 3 to 6 carbon atoms, andspecific examples thereof include cyclopentane and cyclohexane. As thepolycyclic group, a group in which two hydrogen atoms have been removedfrom a polycycloalkane is preferable, and the polycyclic grouppreferably has 7 to 12 carbon atoms. Examples of the polycycloalkaneinclude adamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

The alicyclic hydrocarbon group may or may not have a substituent.Examples of the substituent include an alkyl group of 1 to 5 carbonatoms, a fluorine atom, a fluorinated alkyl group of 1 to 5 carbonatoms, and an oxygen atom (═O).

The aromatic hydrocarbon group as the divalent hydrocarbon group for R²is a hydrocarbon group having an aromatic ring.

The aromatic hydrocarbon ring preferably has 3 to 30 carbon atoms, morepreferably 5 to 30, still more preferably 5 to 20, still more preferably6 to 15, and most preferably 6 to 10. Here, the number of carbon atomswithin a substituent(s) is not included in the number of carbon atoms ofthe aromatic hydrocarbon group.

Examples of the aromatic ring contained in the aromatic hydrocarbongroup include aromatic hydrocarbon rings, such as benzene, biphenyl,fluorene, naphthalene, anthracene and phenanthrene; and aromatic heterorings in which part of the carbon atoms constituting the aforementionedaromatic hydrocarbon rings has been substituted with a hetero atom.

Examples of the hetero atom within the aromatic hetero rings include anoxygen atom, a sulfur atom and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the aforementionedaromatic hydrocarbon ring (arylene group); and a group in which onehydrogen atom has been removed from the aforementioned aromatichydrocarbon ring (aryl group) and one hydrogen atom has been substitutedwith an alkylene group (such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

The aromatic hydrocarbon group may or may not have a substituent. Forexample, the hydrogen atom bonded to the aromatic hydrocarbon ringwithin the aromatic hydrocarbon group may be substituted with asubstituent. Examples of substituents include an alkyl group, an alkoxygroup, a halogen atom, a halogenated alkyl group, a hydroxyl group andan oxygen atom (═O).

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

(Divalent Linking Group Containing a Hetero Atom)

With respect to a “divalent linking group containing a hetero atom” forR², a hetero atom is an atom other than carbon and hydrogen, andexamples thereof include an oxygen atom, a nitrogen atom, a sulfur atomand a halogen atom.

Examples of the divalent linking group containing a hetero atom include—O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH— (H may besubstituted with a substituent such as an alkyl group or an acyl group),—S—, —S(═O)₂—, —S(═O)₂—O—, —NH—C(═O)—, ═N—, and a group represented bygeneral formula —Y²¹—O—Y²²—, —[Y²¹—C(═O)—O]_(m′)—Y²²—, —C(═O)—O—Y²²— or—Y²¹—O—C(═O)—Y²²— [in the formulae, each of Y²¹ and Y²² independentlyrepresents a divalent hydrocarbon group which may have a substituent; Orepresents an oxygen atom; and m′ represents an integer of 0 to 3].

When R² represents —NH—, H may be replaced with a substituent such as analkyl group, an acyl group or the like. The substituent (an alkyl group,an acyl group or the like) preferably has 1 to 10 carbon atoms, morepreferably 1 to 8, and most preferably 1 to 5.

Each of Y²¹ and Y²² independently represents a divalent hydrocarbongroup which may have a substituent. As the divalent hydrocarbon group,the same groups as those described above for the “divalent hydrocarbongroup which may have a substituent” for R² can be mentioned.

As Y²¹, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula —[Y²¹—C(═O)—O]_(m′)—Y²²—, m′represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1. Namely, it is particularlydesirable that the group represented by the formula—[Y²¹—C(═O)—O]_(m′)—Y²² is a group represented by the formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by the formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′ is aninteger of 1 to 10, preferably an integer of 1 to 8, more preferably aninteger of 1 to 5, still more preferably 1 or 2, and most preferably 1.b′ is an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1.

As the divalent linking group containing a hetero atom, a linear groupcontaining an oxygen atom as the hetero atom e.g., a group containing anether bond or an ester bond is preferable, and a group represented bythe aforementioned formula —Y²¹—O—Y²²—, —[Y²¹—C(═O)—O]_(m′)—Y²²—,—C(═O)—O—Y²²— or —Y²¹—O—C(═O)—Y²²— is more preferable.

Among these, as R², a single bond or a divalent linking group containinga hetero atom is preferable, a single bond, a group represented by theaforementioned formula —Y²¹—O—Y²²—, a group represented by theaforementioned formula —[Y²¹—C(═O)—O]_(m′)—Y²²— or a group representedby the aforementioned formula —C(═O)—O—Y²²— or a group represented bythe aforementioned formula —Y²¹—O—C(═O)—Y²²— is more preferable, asingle bond or —C(═O)—O—Y²²— is most preferable.

In the formula (a5-0), Y represents an aromatic hydrocarbon group or analiphatic hydrocarbon group having a polycyclic group, provided that thearomatic hydrocarbon group or the aliphatic hydrocarbon may have acarbon atom or a hydrogen atom thereof substituted with a substituent.

Examples of the aromatic hydrocarbon group for Y include groups in whichone hydrogen atom has been removed from the aromatic ring (aromatichydrocarbon ring) explained above for R²; and groups in which onehydrogen atom of the hydrocarbon ring has been substituted with analkylene group (e.g., arylalkyl groups, such as a benzyl group, aphenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a1-naphthylethyl group, and a 2-naphthylethyl group).

The alkylene group (alkyl chain within the arylalkyl group) preferablyhas 1 to 4 carbon atom, more preferably 1 or 2, and most preferably 1.

Among these, as the aromatic hydrocarbon group for Y, a group in whichone hydrogen atom has been removed from an aromatic ring (aromatichydrocarbon ring) is preferable, and a phenyl group or a naphthyl groupis particularly desirable.

The aromatic hydrocarbon group for Y may have a carbon atom or ahydrogen atom thereof substituted with a substituent. The substituentincludes atoms and atomic groups.

As an example of the aromatic hydrocarbon group in which a carbon atomhas been substituted with a substituent, an aromatic heterocyclic groupin which part of carbon atoms constituting an aromatic hydrocarbon ringhas been substituted with a hetero atom can be mentioned. Examples ofthe hetero atom within the aromatic heterocyclic group include an oxygenatom, a sulfur atom and a nitrogen atom.

In the case where a hydrogen atom of the aromatic hydrocarbon group issubstituted with a substituent, examples of the substituent include analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxy group, an oxygen atom (═O), and an amino group-containinggroup such as —NH₂ or —SO₂—NH₂.

As the alkyl group for the substituent, an alkyl group of 1 to 5 carbonatoms is preferable, a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is more preferable, and a methylgroup is particularly desirable.

The alkoxy group as a substituent is preferably an alkoxy group having 1to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, ann-propoxy group, an iso-propoxy group, an n-butoxy group or atert-butoxy group, and most preferably a methoxy group or an ethoxygroup.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom or a bromine atom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned “alkyl groups for the substituent” has been substitutedwith the aforementioned halogen atoms.

As the aliphatic hydrocarbon group having a polycyclic group for Y, amonovalent group having a polycyclic group among the “aliphatichydrocarbon group containing a ring in the structure thereof” for R² canbe given. Specifically, among the groups mentioned above in theexplanation of R², monovalent groups such as

a group in which one hydrogen atom has been removed from an alicyclichydrocarbon group (aliphatic hydrocarbon ring),

a group in which an alicyclic hydrocarbon group is bonded to a terminalof a linear or branched aliphatic hydrocarbon group, and

a group in which an alicyclic hydrocarbon group is interposed within alinear or branched aliphatic hydrocarbon group

can be given.

Among these, as the aliphatic hydrocarbon group having a polycyclicgroup for Y, a group in which one hydrogen atom has been removed from analicyclic hydrocarbon group (aliphatic hydrocarbon ring) or a group inwhich an alicyclic hydrocarbon group is bonded to a terminal of a linearor branched aliphatic hydrocarbon group is preferable. In such a case,as the alicyclic hydrocarbon group, a group in which one hydrogen atomhas been removed from a polycycloalkane is preferable, and thepolycyclic group preferably has 3 to 20 carbon atoms, more preferably 7to 12 carbon atoms. Specific examples include adamantane, norbornane,isobornane, tricyclodecane and tetracyclododecane.

The aliphatic hydrocarbon group having a polycyclic group for Y may havea carbon atom or a hydrogen atom thereof substituted with a substituent.The substituent includes atoms and atomic groups.

As an example of the aromatic hydrocarbon group in which a carbon atomhas been substituted with a substituent, an aromatic heterocyclic groupin which part of carbon atoms constituting an aromatic hydrocarbon ringhas been substituted with a hetero atom can be mentioned. Examples ofthe hetero atom within the hetero rings include an oxygen atom, a sulfuratom and a nitrogen atom.

In the case where a hydrogen atom of the aliphatic hydrocarbon group issubstituted with a substituent, examples of the substituent include analkyl group of 1 to 5 carbon atoms, a fluorine atom, a fluorinated alkylgroup of 1 to 5 carbon atoms, and an oxygen atom (═O).

In terms of obtaining excellent lithography properties, as thestructural unit (a5), a structural unit represented by general formula(a5-1) or (a5-2) shown below is preferable.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R¹represents a sulfur atom or an oxygen atom; Y^(a) represents an aromatichydrocarbon group (the aromatic hydrocarbon group may have a carbon atomor a hydrogen atom thereof substituted with a substituent); Y^(b)represents an aliphatic hydrocarbon group having a polycyclic group (thealiphatic hydrocarbon group may have a carbon atom or a hydrogen atomthereof substituted with a substituent); each of d1 and d2 independentlyrepresents 0 or 1; and each of e1 and e2 independently represent aninteger of 1 to 5.

In the formulae (a5-1) and (a5-2), R is the same as defined for R in theaforementioned formula (a5-0). R¹ represents a sulfur atom or an oxygenatom, and an oxygen atom is preferable.

In the formula (a5-1), Y^(a) is the same as defined for the aromatichydrocarbon group for Y in the aforementioned formula (a5-0). As Y^(a),a group in which one hydrogen atom has been removed from an aromaticring (aromatic hydrocarbon ring) is preferable, and a phenyl group or anaphthyl group is particularly desirable.

The aromatic hydrocarbon group for Y^(a) preferably has a hydrogen atomthereof substituted with a substituent, and more preferably a hydrogenatom is substituted with a halogen atom. The halogen atom is preferablya fluorine atom or a bromine atom.

In the formula (a5-2), Y^(b) is the same as defined for the aliphatichydrocarbon group having a polycyclic group for Y in the aforementionedformula (a5-0). As Y^(b), a group in which one hydrogen atom has beenremoved from an alicyclic hydrocarbon group (aliphatic hydrocarbon ring)or a group in which an alicyclic hydrocarbon group is bonded to aterminal of a linear or branched aliphatic hydrocarbon group ispreferable.

Specific examples of the structural units represented by generalformulae a5-1) and (a5-2) are shown below.

In the formulae shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

As the structural unit (a5), at least one member selected from the groupconsisting of a structural unit represented by general formula (a5-1)and a structural unit represented by general formula (a5-2) ispreferable.

Among these, at least one member selected from the group consisting of astructural unit represented by any one of formulae (a5-1-1) to (a5-1-5)and a structural unit represented by any one of formulae (a5-2-1) to(a5-2-4) is more preferable.

In the component (A1-1), as the structural unit (a5), one type ofstructural unit may be used alone, or two or more types of structuralunits may be used in combination.

In the component (A1-1), the amount of the structural unit (a5) based onthe combined total of all structural units constituting the component(A1-1) is preferably 5 to 95 mol %, more preferably 5 to 80 mol %, stillmore preferably 10 to 70 mol %, and most preferably 10 to 65 mol %.

When the amount of the structural unit (a5) is at least as large as thelower limit of the above-mentioned range, sensitivity, resolution andlithography properties can be more reliably improved. On the other hand,when the amount of the structural unit (a5) is no more than the upperlimit of the above-mentioned range, a good balance can be reliablyachieved with the other structural units.

Structural Unit (a1)

In the present invention, the structural unit (a1) is a structural unitcontaining an acid decomposable group that exhibits increased polarityby the action of acid.

In the structural unit (a1), the term “acid decomposable group” refersto a group in which at least a part of the bond within the structurethereof is cleaved by the action of an acid.

Examples of acid decomposable groups which exhibit increased polarity bythe action of an acid include groups which are decomposed by the actionof an acid to form a polar group.

Examples of the polar group include a carboxy group, a hydroxy group, anamino group and a sulfo group (—SO₃H). Among these, a polar groupcontaining —OH in the structure thereof (hereafter, referred to as“OH-containing polar group”) is preferable, a carboxy group or a hydroxygroup is more preferable, and a carboxy group is particularly desirable.

More specifically, as an example of an acid decomposable group, a groupin which the aforementioned polar group has been protected with an aciddissociable group (such as a group in which the hydrogen atom of theOH-containing polar group has been protected with an acid dissociablegroup) can be given.

An “acid dissociable group” is a group in which at least the bondbetween the acid dissociable group and the adjacent carbon atom iscleaved by the action of acid. It is necessary that the acid dissociablegroup that constitutes the acid decomposable group is a group whichexhibits a lower polarity than the polar group generated by thedissociation of the acid dissociable group. Thus, when the aciddissociable group is dissociated by the action of acid, a polar groupexhibiting a higher polarity than that of the acid dissociable group isgenerated, thereby increasing the polarity. As a result, the polarity ofthe entire component (A1-1) is increased. By the increase in thepolarity, the solubility in an alkali developing solution changes and,the solubility in an alkali developing solution is relatively increased,whereas the solubility in a developing solution containing an organicsolvent (organic solvent) is relatively decreased.

The acid dissociable group is not particularly limited, and any of thegroups that have been conventionally proposed as acid dissociable groupsfor the base resins of chemically amplified resists can be used.Generally, groups that form either a cyclic or chain-like tertiary alkylester with the carboxyl group of the (meth)acrylic acid, and acetal-typeacid dissociable groups such as alkoxyalkyl groups are widely known.

Here, a tertiary alkyl ester describes a structure in which an ester isformed by substituting the hydrogen atom of a carboxyl group with achain-like or cyclic tertiary alkyl group, and a tertiary carbon atomwithin the chain-like or cyclic tertiary alkyl group is bonded to theoxygen atom at the terminal of the carbonyloxy group (—C(═O)—O—). Inthis tertiary alkyl ester, the action of acid causes cleavage of thebond between the oxygen atom and the tertiary carbon atom, therebyforming a carboxy group.

The chain-like or cyclic alkyl group may have a substituent.

Hereafter, for the sake of simplicity, groups that exhibit aciddissociability as a result of the formation of a tertiary alkyl esterwith a carboxyl group are referred to as “tertiary alkyl ester-type aciddissociable groups”.

Examples of tertiary alkyl ester-type acid dissociable groups includealiphatic branched, acid dissociable groups and aliphatic cyclicgroup-containing acid dissociable groups.

The term “aliphatic branched” refers to a branched structure having noaromaticity. The “aliphatic branched, acid dissociable group” is notlimited to be constituted of only carbon atoms and hydrogen atoms (notlimited to hydrocarbon groups), but is preferably a hydrocarbon group.Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated.

As an example of the aliphatic branched, acid dissociable group, forexample, a group represented by the formula —C(R⁷¹)(R⁷²)(R⁷³) can begiven (in the formula, each of R⁷¹ to R⁷³ independently represents alinear alkyl group of 1 to 5 carbon atoms). The group represented by theformula —C(R⁷¹)(R⁷²)(R⁷³) preferably has 4 to 8 carbon atoms, andspecific examples include a tert-butyl group, a 2-methyl-2-butyl group,a 2-methyl-2-pentyl group and a 3-methyl-3-pentyl group.

Among these, a tert-butyl group is particularly desirable.

The term “aliphatic cyclic group” refers to a monocyclic group orpolycyclic group that has no aromaticity.

In the “aliphatic cyclic group-containing acid dissociable group”, the“aliphatic cyclic group” may or may not have a substituent. Examples ofthe substituent include an alkyl group of 1 to 5 carbon atoms, an alkoxygroup of 1 to 5 carbon atoms, a fluorine atom, a fluorinated alkyl groupof 1 to 5 carbon atoms, and an oxygen atom (═O).

The basic ring of the “aliphatic cyclic group” exclusive of substituentsis not limited to be constituted from only carbon and hydrogen (notlimited to hydrocarbon groups), but is preferably a hydrocarbon group.Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated.

The aliphatic cyclic group may be either a monocyclic group or apolycyclic group.

As such aliphatic cyclic groups, groups in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane which may or maynot be substituted with a lower alkyl group, a fluorine atom or afluorinated alkyl group, may be used. Specific examples of aliphaticcyclic hydrocarbon groups include groups in which one or more hydrogenatoms have been removed from a monocycloalkane such as cyclopentane orcyclohexane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane. In these aliphaticcyclic hydrocarbon groups, part of the carbon atoms constituting thering may be replaced with an ethereal oxygen atom (—O—).

Examples of aliphatic cyclic group-containing acid dissociable groupsinclude

(i) a monovalent aliphatic cyclic group in which a substituent (a groupor an atom other than hydrogen) is bonded to the carbon atom on the ringskeleton to which an atom adjacent to the acid dissociable group (e.g.,“—O—” within “—C(═O)—O— group”) is bonded to form a tertiary carbonatom; and

(ii) a group which has a branched alkylene group containing a tertiarycarbon atom, and a monovalent aliphatic cyclic group to which thetertiary carbon atom is bonded.

In the group (i), as the substituent bonded to the carbon atom to whichan atom adjacent to the acid dissociable group on the ring skeleton ofthe aliphatic cyclic group, an alkyl group can be mentioned. Examples ofthe alkyl group include the same groups as those represented by R¹⁴ informulas (1-1) to (1-9) described later.

Specific examples of the group (i) include groups represented by generalformulas (1-1) to (1-9) shown below.

Specific examples of the group (ii) include groups represented bygeneral formulas (2-1) to (2-6) shown below.

In the formulas above, R¹⁴ represents an alkyl group; and g representsan integer of 0 to 8.

In the formulas above, each of R¹⁵ and R¹⁶ independently represents analkyl group.

In formulas (1-1) to (1-9), the alkyl group for R¹⁴ may be linear,branched or cyclic, and is preferably linear or branched.

The linear alkyl group preferably has 1 to 5 carbon atoms, morepreferably 1 to 4, and still more preferably 1 or 2. Specific examplesinclude a methyl group, an ethyl group, an n-propyl group, an n-butylgroup and an n-pentyl group. Among these, a methyl group, an ethyl groupor an n-butyl group is preferable, and a methyl group or an ethyl groupis more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms, and morepreferably 3 to 5. Specific examples of such branched alkyl groupsinclude an isopropyl group, an isobutyl group, a tert-butyl group, anisopentyl group and a neopentyl group, and an isopropyl group isparticularly desirable.

g is preferably an integer of 0 to 3, more preferably 1 to 3, and stillmore preferably 1 or 2.

In formulas (2-1) to (2-6), as the alkyl group for R¹⁵ and R¹⁶, the samealkyl groups as those for R¹⁴ can be used.

In formulas (1-1) to (1-9) and (2-1) to (2-6), part of the carbon atomsconstituting the ring may be replaced with an ethereal oxygen atom(—O—).

Further, in formulas (1-1) to (1-9) and (2-1) to (2-6), one or more ofthe hydrogen atoms bonded to the carbon atoms constituting the ring maybe substituted with a substituent. Examples of the substituent includean alkyl group of 1 to 5 carbon atoms, a fluorine atom and a fluorinatedalkyl group.

An “acetal-type acid dissociable group” generally substitutes a hydrogenatom at the terminal of an OH-containing polar group such as a carboxygroup or hydroxyl group, so as to be bonded with an oxygen atom. Whenacid acts to break the bond between the acetal-type acid dissociablegroup and the oxygen atom to which the acetal-type, acid dissociablegroup is bonded, an OH-containing polar group such as a carboxy group ora hydroxy group is formed.

Examples of acetal-type acid dissociable groups include groupsrepresented by general formula (p1) shown below.

In the formula, R¹′ and R²′ each independently represent a hydrogen atomor an alkyl group of 1 to 5 carbon atoms; n represents an integer of 0to 3; and Y′ represents an alkyl group of 1 to 5 carbon atoms or analiphatic cyclic group.

In general formula (p1), n is preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 0.

Examples of the alkyl group for R¹′ and R²′ include linear or branchedalkyl groups such as a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group and a neopentyl group. Ofthese, a methyl group or an ethyl group is preferable, and a methylgroup is most preferable.

In the present invention, it is preferable that at least one of R¹′ andR²′ be a hydrogen atom. That is, it is preferable that the aciddissociable group (p1) is a group represented by general formula (p1-1)shown below.

In the formula, R¹′, n and Y′ are the same as defined above.

Examples of the alkyl group for Y′ include linear or branched alkylgroups such as a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group and a neopentyl group.

As the aliphatic cyclic group for Y′, any of the aliphaticmonocyclic/polycyclic groups which have been proposed for conventionalArF resists and the like can be appropriately selected for use. Forexample, the same aliphatic cyclic groups described above in connectionwith the “acid dissociable group containing an aliphatic cyclic group”can be used.

Further, as the acetal-type, acid dissociable group, groups representedby general formula (p2) shown below can also be used.

In the formula, R¹⁷ and R¹⁸ each independently represent a linear orbranched alkyl group or a hydrogen atom; and R¹⁹ represents a linear,branched or cyclic alkyl group; or R¹⁷ and R¹⁹ each independentlyrepresents a linear or branched alkylene group, and the terminal of R¹⁷is bonded to the terminal of R¹⁹ to form a ring.

The alkyl group for R¹⁷ and R¹⁸ preferably has 1 to 15 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable.

It is particularly desirable that either one of R¹⁷ and R¹⁸ be ahydrogen atom, and the other be a methyl group.

R¹⁹ represents a linear, branched or cyclic alkyl group which preferablyhas 1 to 15 carbon atoms, and may be any of linear, branched or cyclic.

When R¹⁹ represents a linear or branched alkyl group, it is preferablyan alkyl group of 1 to 5 carbon atoms, more preferably a methyl group oran ethyl group, and most preferably an ethyl group.

When R¹⁹ represents a cycloalkyl group, it preferably has 4 to 15 carbonatoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10carbon atoms. As examples of the cycloalkyl group, groups in which oneor more hydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, which may or may not be substituted with a fluorineatom or a fluorinated alkyl group, may be used. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane and cyclohexane; and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

In general formula (p2) above, R¹⁷ and R¹⁹ may each independentlyrepresent a linear or branched alkylene group (preferably an alkylenegroup of 1 to 5 carbon atoms), and the terminal of R¹⁹ may be bonded tothe terminal of R¹⁷.

In such a case, a cyclic group is formed by R¹⁷, R¹⁹, the oxygen atomhaving R¹⁹ bonded thereto, and the carbon atom having the oxygen atomand R¹⁷ bonded thereto. Such a cyclic group is preferably a 4- to7-membered ring, and more preferably a 4- to 6-membered ring. Specificexamples of the cyclic group include tetrahydropyranyl group andtetrahydrofuranyl group.

With respect to the structural unit (a1), there is not particularlimitation to the structure of the other portion, as long as thestructural unit has an acid decomposable group. Preferable examples ofthe structural unit (a1) include a structural unit (a11) derived from anacrylate ester having an acid decomposable group and which may have thehydrogen atom bonded to the carbon atom on the α-position substitutedwith a substituent; a structural unit (a12) derived from hydroxystyrenein which the hydrogen atom of the hydroxy group has been substitutedwith an acid dissociable group or a substituent containing an aciddissociable group, wherein the hydrogen atom bonded to the carbon atomon the α-position may be substituted with a substituent, and a hydrogenatom bonded to the benzene ring may be substituted with a substituentother than a hydroxy group; and a structural unit (a13) derived fromvinyl(hydroxynaphthalene) in which the hydrogen atom of the hydroxygroup has been substituted with an acid dissociable group or asubstituent containing an acid dissociable group, wherein the hydrogenatom bonded to the carbon atom on the α-position may be substituted witha substituent, and a hydrogen atom bonded to the naphthalene ring may besubstituted with a substituent other than a hydroxy group.

Among these, in terms of improving roughness (reducing line widthroughness and line edge roughness), a structural unit (a11) ispreferable, and in terms of suppressing absorption of the exposurelight, a structural unit (a12) or a structural unit (a13) is preferable.

In the present description, the expression “structural unit derived froman acrylate ester” refers to a structural unit that is formed by thecleavage of the ethylenic double bond of an acrylate ester.

An “acrylate ester” refers to a compound in which the terminal hydrogenatom of the carboxy group of acrylic acid (CH₂═CH—COOH) has beensubstituted with an organic group.

The acrylate ester may have the hydrogen atom bonded to the carbon atomon the α-position substituted with a substituent. The substituent thatsubstitutes the hydrogen atom bonded to the carbon atom on theα-position is atom other than hydrogen or a group, and examples thereofinclude an alkyl group of 1 to 5 carbon atoms, a halogenated alkyl groupof 1 to 5 carbon atoms and a hydroxyalkyl group. A carbon atom on theα-position of an acrylate ester refers to the carbon atom bonded to thecarbonyl group, unless specified otherwise.

Hereafter, acrylic acid or an acrylate ester having the hydrogen atombonded to the carbon atom on the α-position substituted with asubstituent is sometimes referred to as “α-substituted acrylic acid” or“α-substituted acrylate ester”. Further, acrylic acid and α-substitutedacrylic acid are collectively referred to as “(α-substituted) acrylicacid”, and acrylate esters and α-substituted acrylate esters arecollectively referred to as “(α-substituted) acrylate ester”.

In the α-substituted acrylate ester, the “alkyl group as the substituenton the α-position” is preferably a linear or branched alkyl group, andspecific examples thereof include a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group and a neopentylgroup.

Specific examples of the halogenated alkyl group of 1 to 5 carbon atomsas the substituent on the α-position include groups in which part or allof the hydrogen atoms of the aforementioned “alkyl group of 1 to 5carbon atoms as the substituent on the α-position” are substituted withhalogen atoms. Examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom isparticularly desirable.

It is preferable that a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms is bonded tothe α-position of the α-substituted acrylate ester, a hydrogen atom, analkyl group of 1 to 5 carbon atoms or a fluorinated alkyl group of 1 to5 carbon atoms is more preferable, and in terms of industrialavailability, a hydrogen atom or a methyl group is the most desirable.

A “structural unit derived from a hydroxystyrene” refers to a structuralunit that is formed by the cleavage of the ethylenic double bond of ahydroxystyrene.

A hydroxystyrene is a compound which has 1 vinyl group and at least 1hydroxy group bonded to a benzene ring. The number of hydroxy groupsbonded to the benzene ring is preferably 1 to 3, and most preferably 1.The bonding position of the hydroxy group on the benzene ring is notparticularly limited. When there is 1 hydroxy group, a para-4th positionfrom the bonding position of the vinyl group is preferable. When thereare 2 or more hydroxy groups, a desired combination of the bondingpositions can be used.

A “structural unit derived from a vinyl(hydroxynaphthalene)” refers to astructural unit that is formed by the cleavage of the ethylenic doublebond of a vinyl(hydroxynaphthalene).

A vinyl(hydroxynaphthalene) is a compound which has 1 vinyl group and atleast 1 hydroxy group bonded to a naphthalene ring. The vinyl group maybe bonded to the 1st or 2nd position of the naphthalene ring. The numberof hydroxy groups bonded to the naphthalene ring is preferably 1 to 3,and most preferably 1. The bonding position of the hydroxy group on thenaphthalene ring is not particularly limited. When the vinyl group isbonded to the 1st or 2nd position of the naphthalene ring, the hydroxygroup is preferably bonded to either one of the 5th to 8th position ofthe naphthalene ring. In particular, when the number of hydroxy group is1, the hydroxy group is preferably bonded to either one of the 5th to7th position of the naphthalene ring, and more preferably the 5th or 6thposition. When there are 2 or more hydroxy groups, a desired combinationof the bonding positions can be used.

(Structural Unit (a11)):

The structural unit (a11) is a structural unit derived from an acrylateester having an acid decomposable group and which may have the hydrogenatom bonded to the carbon atom on the α-position substituted with asubstituent.

Examples of the structural unit (a11) include a structural unitrepresented by general formula (a1-0-1) shown below and a structuralunit represented by general formula (a1-0-2) shown below.

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; X¹represents an acid dissociable group; Y² represents a divalent linkinggroup; and X² represents an acid dissociable group.

In general formula (a1-0-1), examples of the alkyl group of 1 to 5carbon atoms for R include linear or branched alkyl groups such as amethyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group and a neopentyl group.

Examples of the halogenated alkyl group of 1 to 5 carbon atoms for Rinclude groups in which part or all of the hydrogen atoms of theaforementioned alkyl groups of 1 to 5 carbon atoms have been substitutedwith halogen atoms. Examples of the halogen atom include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is particularly desirable.

R is preferably a hydrogen atom, an alkyl group of 1 to 5 carbon atomsor a fluorinated alkyl group of 1 to 5 carbon atoms, and most preferablya hydrogen atom or a methyl group.

X¹ is not particularly limited as long as it is an acid dissociablegroup. Examples thereof include the aforementioned tertiary alkylester-type acid dissociable groups and acetal-type acid dissociablegroups, and tertiary alkyl ester-type acid dissociable groups arepreferable.

In general formula (a1-0-2), R is the same as defined above.

X² is the same as defined for X¹ in general formula (a1-0-1).

The divalent linking group for Y² is not particularly limited, andpreferable examples thereof include a divalent hydrocarbon group whichmay have a substituent and a divalent linking group containing a heteroatom.

Examples of the divalent linking group for Y² include the same divalentlinking groups as those described above for R² in the aforementionedformula (a5-0).

Among these, as Y², a linear or branched alkylene group or a divalentlinking group containing a hetero atom is preferable, and a linear orbranched alkylene group, a group represented by the aforementionedformula —Y²¹—O—Y²²—, a group represented by the aforementioned formula—[Y²¹—C(═O)—O]_(m′)—Y²²—, or a group represented by the aforementionedformula —Y²¹—O—C(═O)—Y²²— is more preferable.

Specific examples of the structural unit (a11) include structural unitsrepresented by general formulas (a1-1) to (a1-4) shown below.

In the formulas, R, R¹′, R²′, n, Y′ and Y² are the same as definedabove; and X′ represents a tertiary alkyl ester-type acid dissociablegroup.In the formulas, the tertiary alkyl ester-type acid dissociable groupfor X′ include the same tertiary alkyl ester-type acid dissociablegroups as those described above.

As R¹′, n and Y′ are respectively the same as defined for R¹′, n and Y′in general formula (p1) described above in connection with the“acetal-type acid dissociable group”.

As examples of Y², the same groups as those described above for Y² ingeneral formula (a1-0-2) can be given.

Specific examples of structural units represented by general formula(a1-1) to (a1-4) are shown below.

In the formulas shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

In the present invention, as the structural unit (a11),

it is preferable to include at least one member selected from the groupconsisting of structural units represented by general formulae (a1-0-11)to (a1-0-15), (a1-2) and (a1-0-2),

and it is more preferable to include at least one member selected fromthe group consisting of a structural unit represented by general formula(a1-0-11), a structural unit represented by general formula (a1-0-12), astructural unit represented by general formula (a1-0-15) and astructural unit represented by general formula (a1-2).

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R²¹represents an alkyl group; R²² represents a group which forms analiphatic monocyclic group with the carbon atom to which R²² is bonded;R²³ represents a branched alkyl group; R²⁴ represents a group whichforms an aliphatic polycyclic group with the carbon atom to which R²⁴ isbonded; R²⁵ represents a linear alkyl group of 1 to 5 carbon atoms; R¹⁵and R¹⁶ each independently represents an alkyl group; each of R¹′ andR²′ independently represents a hydrogen atom or an alkyl group of 1 to 5carbon atoms; n represents an integer of 0 to 3; Y′ represents an alkylgroup of 1 to 5 carbon atoms or an aliphatic cyclic group; Y² representsa divalent linking group; and X² represents an acid dissociable group.

In the formulas, R, Y² and X² are the same as defined above.

In general formula (a1-0-11), as the alkyl group for R²¹, the same alkylgroups as those described above for R¹⁴ in formulas (1-1) to (1-9) canbe used, preferably a methyl group, an ethyl group or an isopropylgroup, and more preferably a methyl group or an ethyl group.

As the aliphatic monocyclic group formed by R²² and the carbon atoms towhich R²² is bonded, the same aliphatic cyclic groups as those describedabove for the aforementioned tertiary alkyl ester-type acid dissociablegroup and which are monocyclic can be used. Specific examples includegroups in which one or more hydrogen atoms have been removed from amonocycloalkane. The monocycloalkane is preferably a 3- to 11-memberedring, more preferably a 3- to 8-membered ring, still more preferably a4- to 6-membered ring, and most preferably a 5- or 6-membered ring.

The monocycloalkane may or may not have part of the carbon atomsconstituting the ring replaced with an ether bond (—O—).

Further, the monocycloalkane may have a substituent such as an alkylgroup of 1 to 5 carbon atoms, a fluorine atom or a fluorinated alkylgroup of 1 to 5 carbon atoms.

As an examples of R²² constituting such an aliphatic cyclic group, analkylene group which may have an ether bond (—O—) interposed between thecarbon atoms can be given.

Specific examples of structural units represented by general formula(a1-0-11) include structural units represented by the aforementionedformulas (a1-1-16) to (a1-1-23), (a1-1-27) and (a1-1-31) to (a1-1-33).Among these, a structural unit represented by general formula (a1-1-02)shown below which includes the structural units represented by theaforementioned formulas (a1-1-16), (a1-1-17), (a1-1-20) to (a1-1-23),(a1-1-27) and (a1-1-31) to (a1-1-33) is preferable. Further, astructural unit represented by general formula (a1-1-02′) shown below isalso preferable.

In the formulas, h is preferably 1 or 2.

In the formulae, R and R²¹ are the same as defined above; and hrepresents an integer of 1 to 4.

In general formula (a1-0-12), as the branched alkyl group for R²³, thesame alkyl groups as those described above for R¹⁴ which are branchedcan be used, and an isopropyl group is particularly desirable.

As the aliphatic polycyclic group formed by R²⁴ and the carbon atoms towhich R²⁴ is bonded, the same aliphatic cyclic groups as those describedabove for the aforementioned tertiary alkyl ester-type acid dissociablegroup and which are polycyclic can be used.

Specific examples of structural units represented by general formula(a1-0-12) include structural units represented by the aforementionedformulas (a1-1-26) and (a1-1-28) to (a1-1-30).

As the structural unit (a1-0-12), a structural unit in which thealiphatic polycyclic group formed by R²⁴ and the carbon atom to whichR²⁴ is bonded is a 2-adamantyl group is preferable, and a structuralunit represented by the aforementioned formula (a1-1-26) is particularlydesirable.

In general formula (a1-0-13), R and R²⁴ are the same as defined above.

As the linear alkyl group for R²⁵, the same linear alkyl groups as thosedescribed above for R¹⁴ in the aforementioned formulas (1-1) to (1-9)can be mentioned, and a methyl group or an ethyl group is particularlydesirable.

Specific examples of structural units represented by general formula(a1-0-13) include structural units represented by the aforementionedformulas (a1-1-1) to (a1-1-3) and (a1-1-7) to (a1-1-15) which weredescribed above as specific examples of the structural unit representedby general formula (a1-1).

As the structural unit (a1-0-13), a structural unit in which thealiphatic polycyclic group formed by R²⁴ and the carbon atom to whichR²⁴ is bonded is a 2-adamantyl group is preferable, and a structuralunit represented by the aforementioned formula (a1-1-1), (a1-1-2) or(a1-1-9) is particularly desirable.

In general formula (a1-0-14), R and R²² are the same as defined above.R¹⁵ and R¹⁶ are the same as R¹⁵ and R¹⁶ in the aforementioned generalformulae (2-1) to (2-6), respectively.

Specific examples of structural units represented by general formula(a1-0-14) include structural units represented by the aforementionedformulae (a1-1-35) and (a1-1-36) which were described above as specificexamples of the structural unit represented by general formula (a1-1).

In general formula (a1-0-15), R and R²⁴ are the same as defined above.R¹⁵ and R¹⁶ are the same as R¹⁵ and R¹⁶ in the aforementioned generalformulae (2-1) to (2-6), respectively.

Specific examples of structural units represented by general formula(a1-0-15) include structural units represented by the aforementionedformulae (a1-1-4) to (a1-1-6) and (a1-1-34) which were described aboveas specific examples of the structural unit represented by generalformula (a1-1).

In formula (a1-2), R¹′, R²′, n and Y′ are the same as defined above.

It is preferable that at least one of R¹′ and R²′ is a hydrogen atom,and it is particularly desirable that both R¹′ and R²′ are hydrogenatoms.

n is more preferably 0 or 1, and most preferably 0.

Y′ is preferably an aliphatic cyclic group, and the same aliphaticcyclic groups as those given as examples for the aforementioned “aciddissociable group containing an aliphatic cyclic group” can bementioned, and a group in which one or more hydrogen atoms have beenremoved from a polycycloalkane is more preferable.

Specific examples of the structural unit represented by formula (a1-2)include a structural unit represented by formula (a1-2-6).

Examples of structural units represented by general formula (a1-0-2)include structural units represented by the aforementioned formulas(a1-3) and (a1-4).

As the structural unit represented by formula (a1-0-2), a structuralunit in which Y² is a group represented by the aforementioned formula—Y²¹—O—Y²²—, a group represented by the aforementioned formula—[Y²¹—C(═O)—O]_(m′)—Y²²— or a group represented by the aforementionedformula —Y²¹—O—C(═O)—Y²²— is particularly desirable.

Preferable examples of such structural units include a structural unitrepresented by general formula (a1-3-01) shown below, a structural unitrepresented by general formula (a1-3-02) shown below, and a structuralunit represented by general formula (a1-3-03) shown below.

In the formulas, R is the same as defined above; R¹³ represents ahydrogen atom or a methyl group; R¹⁴ represents an alkyl group; yrepresents an integer of 1 to 10; and n′ represents an integer of 0 to3.

In the formula, R is as defined above; each of Y²′ and Y²″ independentlyrepresents a divalent linking group; X′ represents an acid dissociablegroup; and w represents an integer of 0 to 3.

In general formulas (a1-3-01) and (a1-3-02), R¹³ is preferably ahydrogen atom.

R¹⁴ is the same as defined for R¹⁴ in the aforementioned formulas (1-1)to (1-9).

w is preferably an integer of 1 to 8, more preferably 1 to 5, and mostpreferably 1 or 2.

n′ is preferably 1 or 2, and most preferably 2.

Specific examples of structural units represented by general formula(a1-3-01) include structural units represented by the aforementionedformulas (a1-3-25) and (a1-3-26).

Specific examples of structural units represented by general formula(a1-3-02) include structural units represented by the aforementionedformulas (a1-3-27) and (a1-3-28).

In general formula (a1-3-03), as the divalent linking group for Y²′ andY²″, the same groups as those described above for Y² in general formula(a1-3) can be used.

As Y²′, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As Y²″, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As the acid dissociable group for X′, the same groups as those describedabove can be used. X′ is preferably a tertiary alkyl ester-type aciddissociable group, more preferably the aforementioned group (i) in whicha substituent is bonded to the carbon atom to which an atom adjacent tothe acid dissociable group is bonded to on the ring skeleton to form atertiary carbon atom. Among these, a group represented by theaforementioned general formula (1-1) is particularly desirable.

w represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1.

As the structural unit represented by general formula (a1-3-03), astructural unit represented by general formula (a1-3-03-1) or(a1-3-03-2) shown below is preferable, and a structural unit representedby general formula (a1-3-03-1) is particularly desirable.

In the formulas, R and R¹⁴ are the same as defined above; a′ representsan integer of 1 to 10; b′ represents an integer of 1 to 10; and trepresents an integer of 0 to 3.

In general formulas (a1-3-03-1) and (a1-3-03-2), a′ is preferably aninteger of 1 to 8, more preferably 1 to 5, and most preferably 1 or 2.

b′ is preferably an integer of 1 to 8, more preferably 1 to 5, and mostpreferably 1 or 2.

t is preferably an integer of 1 to 3, and most preferably 1 or 2.

Specific examples of structural units represented by general formula(a1-3-03-1) or (a1-3-03-2) include structural units represented by theaforementioned formulas (a1-3-29) to (a1-3-32).

(Structural Unit (a12)):

The structural unit (a12) is a structural unit derived fromhydroxystyrene in which the hydrogen atom of the hydroxy group has beensubstituted with an acid dissociable group or a substituent containingan acid dissociable group, wherein the hydrogen atom bonded to thecarbon atom on the α-position may be substituted with a substituent, anda hydrogen atom bonded to the benzene ring may be substituted with asubstituent other than a hydroxy group.

As the acid dissociable group which substitutes the hydrogen atom of thehydroxy group, the same acid dissociable groups as those described abovecan be given, a tertiary alkyl ester-type acid dissociable group or anacetal-type acid dissociable group is preferable, and an acetal-typeacid dissociable group is more preferable.

Examples of the substituent containing an acid dissociable group includea group constituted of an acid dissociable group and a divalent linkinggroup. As the divalent linking group, the same divalent linking groupsas those described above for Y² in the aforementioned formula (a1-0-2)can be given, and a group in which the terminal structure of the aciddissociable group-side is a carbonyloxy group is particularly desirable.In such a case, it is preferable that the acid dissociable group isbonded to the oxygen atom (—O—) of the carbonyloxy group.

As the substituent containing an acid dissociable group, a grouprepresented by formula R¹¹′—O—C(═O)— or a group represented by formulaR¹¹′—O—C(═O)— is preferable. In the formulae, R¹¹′ represents an aciddissociable group, and R¹²′ represents a linear or branched alkylenegroup.

The acid dissociable group for R¹¹′ is preferably a tertiary alkylester-type acid dissociable group or an acetal-type acid dissociablegroup, and more preferably a tertiary alkyl ester-type acid dissociablegroup. Preferable examples of the tertiary alkyl ester-type aciddissociable group include the aforementioned aliphatic branched aciddissociable group represented by the formula —C(R⁷¹)(R⁷²)(R⁷³), a grouprepresented by any one of formulae (1-1) to (1-9), and a grouprepresented by any one of formulae (2-1) to (2-6).

Examples of the alkylene group for R¹²′ include a methylene group, anethylene group, a trimethylene group, a tetramethylene group and a1,1-dimethylethylene group. As R¹²′, a linear alkylene group ispreferable.

(Structural Unit (a13)):

The structural unit (a13) is a structural unit derived fromvinyl(hydroxynaphthalene) in which the hydrogen atom of the hydroxygroup has been substituted with an acid dissociable group or asubstituent containing an acid dissociable group, wherein the hydrogenatom bonded to the carbon atom on the α-position may be substituted witha substituent, and a hydrogen atom bonded to the naphthalene ring may besubstituted with a substituent other than a hydroxy group.

In the structural unit (a13), as the acid dissociable group or thesubstituent containing an acid dissociable group which substitutes thehydrogen atom of the hydroxy group, the same groups as those describedabove for the structural unit (a12) can be mentioned.

When the component (A1-1) has a structural unit (a1), as the structuralunit (a1), one type of structural unit may be used, or two or more typesmay be used.

In the component (A1-1), the amount of the structural unit (a1) based onthe combined total of all structural units constituting the component(A1-1) is preferably 15 to 70 mol %, more preferably 15 to 60 mol %, andstill more preferably 20 to 55 mol %.

When the amount of the structural unit (a1)) is at least as large as thelower limit of the above-mentioned range, a pattern can be easily formedusing a resist composition prepared from the component (A1), and variouslithography properties such as sensitivity, resolution, pattern shapeand the like are improved. On the other hand, when the amount of thestructural unit (a1) is no more than the upper limit of theabove-mentioned range, a good balance can be achieved with the otherstructural units.

Structural Unit (a2)

In the present invention, the structural unit (a2) is a structural unitcontaining a —SO₂— containing cyclic group or a lactone-containingcyclic group.

When the component (A1-1) is used for forming a resist film, the —SO₂—containing cyclic group or the lactone-containing cyclic group withinthe structural unit (a2) is effective in improving the adhesion betweenthe resist film and the substrate.

The aforementioned structural unit (a5) or (a1) which contains a —SO₂—containing cyclic group or a lactone-containing cyclic group falls underthe definition of the structural unit (a2); however, such a structuralunit is regarded as a structural unit (a5) or (a1), and does not fallunder the definition of the structural unit (a2).

Here, an “—SO₂— containing cyclic group” refers to a cyclic group havinga ring containing —SO₂— within the ring structure thereof, i.e., acyclic group in which the sulfur atom (S) within —SO₂— forms part of thering skeleton of the cyclic group. The ring containing —SO₂— within thering skeleton thereof is counted as the first ring. A cyclic group inwhich the only ring structure is the ring that contains —SO₂— in thering skeleton thereof is referred to as a monocyclic group, and a groupcontaining other ring structures is described as a polycyclic groupregardless of the structure of the other rings. The —SO₂— containingcyclic group may be either a monocyclic group or a polycyclic group.

As the —SO₂— containing cyclic group, a cyclic group containing —O—SO₂—within the ring skeleton thereof, i.e., a cyclic group containing asultone ring in which —O—S— within the —O—SO₂— group forms part of thering skeleton thereof is particularly desirable.

The —SO₂— containing cyclic group preferably has 3 to 30 carbon atoms,more preferably 4 to 20, still more preferably 4 to 15, and mostpreferably 4 to 12. Herein, the number of carbon atoms refers to thenumber of carbon atoms constituting the ring skeleton, excluding thenumber of carbon atoms within a substituent.

The —SO₂— containing cyclic group may be either a —SO₂— containingaliphatic cyclic group or a —SO₂— containing aromatic cyclic group. A—SO₂— containing aliphatic cyclic group is preferable.

Examples of the —SO₂— containing aliphatic cyclic group includealiphatic cyclic groups in which part of the carbon atoms constitutingthe ring skeleton has been substituted with a —SO₂— group or a —O—SO₂—group and has at least one hydrogen atom removed from the aliphatichydrocarbon ring. Specific examples include an aliphatic hydrocarbonring in which a —CH₂— group constituting the ring skeleton thereof hasbeen substituted with a —SO₂— group and has at least one hydrogen atomremoved therefrom; and an aliphatic hydrocarbon ring in which a—CH₂—CH₂— group constituting the ring skeleton has been substituted witha —O—SO₂— group and has at least one hydrogen atom removed therefrom.

The alicyclic hydrocarbon ring preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon ring may be either a monocyclic group or apolycyclic group. As the monocyclic group, a group in which two hydrogenatoms have been removed from a monocycloalkane of 3 to 6 carbon atoms ispreferable. Examples of the monocycloalkane include cyclopentane andcyclohexane. As the polycyclic group, a group in which two hydrogenatoms have been removed from a polycycloalkane of 7 to 12 carbon atomsis preferable. Examples of the polycycloalkane include adamantane,norbornane, isobornane, tricyclodecane and tetracyclododecane.

The —SO₂— containing cyclic group may have a substituent. Examples ofthe substituent include an alkyl group, an alkoxy group, a halogen atom,a halogenated alkyl group, a hydroxy group, an oxygen atom (═O), —COOR″,—OC(═O)R″, a hydroxyalkyl group and a cyano group.

The alkyl group for the substituent is preferably an alkyl group of 1 to6 carbon atoms. Further, the alkyl group is preferably a linear alkylgroup or a branched alkyl group. Specific examples include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, a neopentyl group and a hexyl group. Among these, amethyl group or ethyl group is preferable, and a methyl group isparticularly desirable.

As the alkoxy group for the substituent, an alkoxy group of 1 to 6carbon atoms is preferable. Further, the alkoxy group is preferably alinear or branched alkoxy group. Specific examples of the alkoxy groupinclude the aforementioned alkyl groups for the substituent having anoxygen atom (—O—) bonded thereto.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

As examples of the halogenated alkyl group for the substituent, groupsin which part or all of the hydrogen atoms of the aforementioned alkylgroups for the substituent have been substituted with the aforementionedhalogen atoms can be given. As the halogenated alkyl group, afluorinated alkyl group is preferable, and a perfluoroalkyl group isparticularly desirable.

In the —COOR″ group and the —OC(═O)R″ group, R″ represents a hydrogenatom or a linear, branched or cyclic alkyl group of 1 to 15 carbonatoms.

When R″ represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and mostpreferably 5 to 10 carbon atoms. As examples of the cycloalkyl group,groups in which one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane, which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group, may be used. Specificexamples include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane such as cyclopentane and cyclohexane; andgroups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

The hydroxyalkyl group for the substituent preferably has 1 to 6 carbonatoms, and specific examples thereof include the aforementioned alkylgroups for the substituent in which at least one hydrogen atom has beensubstituted with a hydroxy group.

More specific examples of the —SO₂— containing cyclic group includegroups represented by general formulas (3-1) to (3-4) shown below.

In the formulas, A′ represents an oxygen atom, a sulfur atom or analkylene group of 1 to 5 carbon atoms which may contain an oxygen atomor a sulfur atom; z represents an integer of 0 to 2; and R²⁷ representsan alkyl group, an alkoxy group, a halogenated alkyl group, a hydroxylgroup, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyano group, whereinR″ represents a hydrogen atom or an alkyl group.

In general formulas (3-1) to (3-4) above, A′ represents an oxygen atom(—O—), a sulfur atom (—S—) or an alkylene group of 1 to 5 carbon atomswhich may contain an oxygen atom or a sulfur atom.

As the alkylene group of 1 to 5 carbon atoms represented by A′, a linearor branched alkylene group is preferable, and examples thereof include amethylene group, an ethylene group, an n-propylene group and anisopropylene group.

Examples of alkylene groups that contain an oxygen atom or a sulfur atominclude the aforementioned alkylene groups in which —O— or —S— is bondedto the terminal of the alkylene group or present between the carbonatoms of the alkylene group. Specific examples of such alkylene groupsinclude —O—CH₂—, —CH₂—O—CH₂—, —S—CH₂—, —CH₂—S—CH₂—.

As A′, an alkylene group of 1 to 5 carbon atoms or —O— is preferable,more preferably an alkylene group of 1 to 5 carbon atoms, and mostpreferably a methylene group.

z represents an integer of 0 to 2, and is most preferably 0.

When z is 2, the plurality of R²⁷ may be the same or different from eachother.

As the alkyl group, alkoxy group, halogenated alkyl group, —COOR″,—OC(═O)R″ and hydroxyalkyl group for R²⁷, the same alkyl groups, alkoxygroups, halogenated alkyl groups, —COOR″, —OC(═O)R″ and hydroxyalkylgroups as those described above as the substituent for the —SO₂—containing cyclic group can be mentioned.

Specific examples of the cyclic groups represented by general formulas(3-1) to (3-4) are shown below. In the formulas shown below, “Ac”represents an acetyl group.

As the —SO₂— containing cyclic group, a group represented by theaforementioned general formula (3-1) is preferable, at least one memberselected from the group consisting of groups represented by theaforementioned chemical formulas (3-1-1), (3-1-18), (3-3-1) and (3-4-1)is more preferable, and a group represented by chemical formula (3-1-1)is most preferable.

The term “lactone-containing cyclic group” refers to a cyclic groupincluding a ring containing a —O—C(═O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings. The lactone-containing cyclic groupmay be either a monocyclic group or a polycyclic group.

The lactone-containing cyclic group for the structural unit (a2) is notparticularly limited, and an arbitrary structural unit may be used.Specific examples of lactone-containing monocyclic groups include agroup in which one hydrogen atom has been removed from a 4- to6-membered lactone ring, such as a group in which one hydrogen atom hasbeen removed from β-propionolatone, a group in which one hydrogen atomhas been removed from γ-butyrolactone, and a group in which one hydrogenatom has been removed from δ-valerolactone. Further, specific examplesof lactone-containing polycyclic groups include groups in which onehydrogen atom has been removed from a lactone ring-containingbicycloalkane, tricycloalkane or tetracycloalkane.

With respect to the structural unit (a2), there is not particularlimitation to the structure of the other portion, as long as thestructural unit has a —SO₂— containing cyclic group or alactone-containing cyclic group. The structural unit (a2) is preferablyat least one structural unit selected from the group consisting of astructural unit (a2^(S)) derived from an acrylate ester which may havethe hydrogen atom bonded to the carbon atom on the α-positionsubstituted with a substituent and contains an —SO₂— containing cyclicgroup, and a structural unit (a2^(L)) derived from an acrylate esterwhich may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent and contains alactone-containing cyclic group.

Structural Unit (a2^(S)):

More specific examples of the structural unit (a2^(S)) includestructural units represented by general formula (a2-0) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R²⁶represents —O— or —NH—; R²⁸ represents a —SO₂— containing cyclic group;and R²⁹ represents a single bond or a divalent linking group.

In general formula (a2-0), R is the same as defined above.

R²⁶ represents —O— or —NH—.

R²⁸ is the same as defined for the aforementioned —SO₂— containinggroup.

R²⁹ may be either a single bond or a divalent linking group. In terms ofthe effects of the present invention, a divalent linking group ispreferable.

The divalent linking group for R²⁹ is not particularly limited, andexamples thereof include the same divalent linking groups as thosedescribed above for R² in the aforementioned formula (a5-0). Amongthese, an alkylene group or a divalent linking group containing an esterbond (—C(═O)—O—) is preferable.

As the alkylene group, a linear or branched alkylene group ispreferable. Specific examples include the same linear alkylene groupsand branched alkylene groups as those described above for the aliphatichydrocarbon group represented by R² in the aforementioned formula(a5-0).

As the divalent linking group containing an ester bond, a grouprepresented by general formula: —R³⁰—C(═O)—O— (in the formula, R³⁰represents a divalent linking group) is particularly desirable. That is,the structural unit (a2^(S)) is preferably a structural unit representedby general formula (a2-0-1) shown below.

In the formula, R, R²⁶ and R²⁸ are the same as defined above; and R³⁰represents a divalent linking group.

R³⁰ is not particularly limited, and examples thereof include the samedivalent linking groups as those described above for R² in theaforementioned formula (a5-0).

As the divalent linking group for R³⁰, a linear or branched alkylenegroup, an aliphatic hydrocarbon group having a ring in the structurethereof, or a divalent linking group containing a hetero atom ispreferable, and a linear or branched alkylene group or a divalentlinking group containing a hetero atom is more preferable.

As the linear alkylene group, a methylene group or an ethylene group ispreferable, and a methylene group is particularly desirable.

As the branched alkylene group, an alkylmethylene group or analkylethylene group is preferable, and —CH(CH₃)—, —C(CH₃)₂— or—C(CH₃)₂CH₂— is particularly desirable. As the divalent linking groupcontaining a hetero atom, a divalent linking group containing an etherbond or an ester bond is preferable, and a group represented by theaforementioned formula —Y²¹—O—Y²²—, —[Y²¹—C(═O)—O]_(m′)—Y²²— or—Y²¹—O—C(═O)—Y²²— is more preferable. Each of Y²¹ and Y²² independentlyrepresents a divalent hydrocarbon group which may have a substituent;and m′ represents an integer of 0 to 3. Among these, —Y²¹—O—C(═O)—Y²²—is preferable, and a group represented by the formula—(CH₂)_(c)—O—C(═O)—(CH₂)_(d)— is particularly desirable. c represents aninteger of 1 to 5, and preferably 1 or 2. d represents an integer of 1to 5, and preferably 1 or 2.

In particular, as the structural unit (a2^(S)), a structural unitrepresented by general formula (a2-0-11) or (a2-0-12) shown below ispreferable, and a structural unit represented by general formula(a2-0-12) shown below is more preferable.

In the formulae, R, A′, R²⁶, R²⁷, z and R³⁰ are the same as definedabove.

In general formula (a2-0-11), A′ is preferably a methylene group, anoxygen atom (—O—) or a sulfur atom (—S—).

As R³⁰, a linear or branched alkylene group or a divalent linking groupcontaining an oxygen atom is preferable. As the linear or branchedalkylene group and the divalent linking group containing an oxygen atomrepresented by R³⁰, the same linear or branched alkylene groups and thedivalent linking groups containing an oxygen atom as those describedabove can be mentioned.

As the structural unit represented by general formula (a2-0-12), astructural unit represented by general formula (a2-0-12a) or (a2-0-12b)shown below is particularly desirable.

In the formulae, R, R²⁶ and A′ are the same as defined above; and eachof c, d and f independently represents an integer of 1 to 3.

Structural Unit (a2^(L)):

Examples of the structural unit (a2^(L)) include structural unitsrepresented by the aforementioned general formula (a2-0) in which theR²⁸ group has been substituted with a lactone-containing cyclic group.Specific examples include structural units represented by generalformulas (a2-1) to (a2-5) shown below.

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; eachR′ independently represents a hydrogen atom, an alkyl group, an alkoxygroup, a halogenated alkyl group, a hydroxy group, —COOR″, OC(═O)R″, ahydroxyalkyl group or a cyano group, wherein R″ represents a hydrogenatom or an alkyl group; R²⁹ represents a single bond or a divalentlinking group; s″ represents an integer of 0 to 2; A″ represents anoxygen atom, a sulfur atom or an alkylene group of 1 to 5 carbon atomswhich may contain an oxygen atom or a sulfur atom; and m represents 0 or1.

In general formulas (a2-1) to (a2-5), R is the same as defined above.

As the alkyl group, alkoxy group, halogenated alkyl group, —COOR″,—OC(═O)R″ and hydroxyalkyl group for R′, the same alkyl groups, alkoxygroups, halogenated alkyl groups, —COOR″, —OC(═O)R″ and hydroxyalkylgroups as those described above as the substituent for the —SO₂—containing cyclic group can be mentioned.

In terms of industrial availability, R′ is preferably a hydrogen atom.

The alkyl group for R″ may be any of linear, branched or cyclic.

When R″ is a linear or branched alkyl group, it preferably has 1 to 10carbon atoms, more preferably 1 to 5 carbon atoms.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and mostpreferably 5 to 10 carbon atoms. As examples of the cycloalkyl group,groups in which one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane, which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group, may be used. Examplesof such groups include groups in which one or more hydrogen atoms havebeen removed from a monocycloalkane such as cyclopentane or cyclohexane;and groups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

As examples of A″, the same groups as those described above for A′ ingeneral formula (3-1) can be given. A″ is preferably an alkylene groupof 1 to 5 carbon atoms, an oxygen atom (—O—) or a sulfur atom (—S—), andmore preferably an alkylene group of 1 to 5 carbon atoms or —O—. As thealkylene group of 1 to 5 carbon atoms, a methylene group or adimethylethylene group is preferable, and a methylene group isparticularly desirable.

R²⁹ is the same as defined for R²⁹ in the aforementioned general formula(a2-0).

In formula (a2-1), s″ is preferably 1 or 2.

Specific examples of structural units represented by general formulas(a2-1) to (a2-5) are shown below. In the formulae shown below, R^(α)represents a hydrogen atom, a methyl group or a trifluoromethyl group.

As the structural unit (a2^(L)), it is preferable to include at leastone structural unit selected from the group consisting of structuralunits represented by the aforementioned general formulas (a2-1) to(a2-5), more preferably at least one structural unit selected from thegroup consisting of structural units represented by the aforementionedgeneral formulas (a2-1) to (a2-3), and most preferably at least onestructural unit selected from the group consisting of structural unitsrepresented by the aforementioned general formulas (a2-1) and (a2-3).

Specifically, it is preferable to use at least one structural unitselected from the group consisting of formulae (a2-1-1), (a2-1-2),(a2-2-1), (a2-2-7), (a2-2-12), (a2-2-13), (a2-2-15), (a2-3-1) and(a2-3-5).

Further, as the structural unit (a2^(L)), a structural unit representedby general formula (a2-6) or (a2-7) shown below is also preferable.

In the formulae, R and R²⁹ are the same as defined above.

When the component (A1-1) has a structural unit (a2), as the structuralunit (a2), one type of structural unit may be used, or two or more typesmay be used. For example, as the structural unit (a2), a structural unit(a2^(S)) may be used alone, or a structural unit (a2^(L)), or acombination of these structural units may be used. Further, as thestructural unit (a2⁵) or the structural unit (a2^(L)), either a singletype of structural unit may be used, or two or more types may be used incombination.

In the component (A1-1), the amount of the structural unit (a2) based onthe combined total of all structural units constituting the component(A1-1) is preferably 1 to 80 mol %, more preferably 10 to 70 mol %,still more preferably 10 to 65 mol %, and most preferably 10 to 60 mol%.

When the amount of the structural unit (a2) is at least as large as thelower limit of the above-mentioned range, the effect of using thestructural unit (a2) can be satisfactorily achieved. On the other hand,when the amount of the structural unit (a2) is no more than the upperlimit of the above-mentioned range, a good balance can be achieved withthe other structural units, and various lithography properties andpattern shape can be improved.

Structural Unit (a3)

In the present invention, the structural unit (a3) is a structural unitcontaining a polar group.

When the component (A1-1) includes the structural unit (a3), thepolarity of the component (A1-1) after exposure is further increased.Increase in the polarity of the component (A1-1) as the base resincontributes to improvement in terms of resolution and the like,particularly in an alkali developing process.

Examples of the polar group include —OH, —COOH, —CN, —SO₂NH₂ and —CONH₂.Structural units that contain —COOH include structural units of(α-substituted) acrylic acid.

The structural unit (a3) is preferably a structural unit containing ahydrocarbon group in which part of the hydrogen atoms has beensubstituted with a polar group. The hydrocarbon group may be either analiphatic hydrocarbon group or an aromatic hydrocarbon group. Amongthese, as the hydrocarbon group, an aliphatic hydrocarbon group ispreferable.

Examples of the aliphatic hydrocarbon group as the hydrocarbon groupinclude linear or branched hydrocarbon groups (preferably alkylenegroups) of 1 to 10 carbon atoms, and aliphatic cyclic groups (monocyclicgroups and polycyclic groups).

These aliphatic cyclic groups (monocyclic groups and polycyclic groups)can be selected appropriately from the multitude of groups that havebeen proposed for the resins of resist compositions designed for usewith ArF excimer lasers. The aliphatic cyclic group preferably has 3 to30 carbon atoms, more preferably 5 to 30, still more preferably 5 to 20,still more preferably 6 to 15, and most preferably 6 to 12. As thealiphatic cyclic group, a group in which two or more hydrogen atoms havebeen removed from a monocycloalkane or a polycycloalkane such as abicycloalkane, tricycloalkane or tetracycloalkane can be used. Specificexamples include groups in which two or more hydrogen atoms have beenremoved from a monocycloalkane such as cyclopentane or cyclohexane; andgroups in which two or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane. The aliphatic cyclic group may ormay not have a substituent. Examples of the substituent include an alkylgroup of 1 to 5 carbon atoms, a fluorine atom, and a fluorinated alkylgroup of 1 to 5 carbon atoms.

The aromatic hydrocarbon group as the hydrocarbon group is a hydrocarbongroup having at least one aromatic ring.

The aromatic ring is not particularly limited, as long as it is a cyclicconjugated compound having 4n+2π electrons (wherein n represents 0 or anatural number), and may be either monocyclic or polycyclic. Thearomatic ring preferably has 5 to 30 carbon atoms, more preferably 5 to20, still more preferably 6 to 15, and most preferably 6 to 12. Here,the number of carbon atoms within a substituent(s) is not included inthe number of carbon atoms of the aromatic hydrocarbon group. Examplesof the aromatic ring include aromatic hydrocarbon rings, such asbenzene, naphthalene, anthracene and phenanthrene; and aromatic heterorings in which part of the carbon atoms constituting the aforementionedaromatic hydrocarbon rings has been substituted with a hetero atom.Examples of the hetero atom within the aromatic hetero rings include anoxygen atom, a sulfur atom and a nitrogen atom. Specific examples of thearomatic hetero ring include a pyridine ring and a thiophene ring.

Specific examples of the aromatic hydrocarbon group as the divalenthydrocarbon group include a group in which two or more hydrogen atomshave been removed from the aforementioned aromatic hydrocarbon ring oraromatic hetero ring (arylene group or heteroarylene group); a group inwhich two ore more hydrogen atoms have been removed from an aromaticcompound having two or more aromatic rings (biphenyl, fluorene or thelike); and a group in which one hydrogen atom of the aforementionedaromatic ring has been substituted with an alkylene group (an arylalkylgroup such as a benzyl group, a phenethyl group, a 1-naphthylmethylgroup, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a2-naphthylethyl group, or a heteroarylalkyl group) and has one hydrogenatom removed from the aromatic ring. The alkylene group whichsubstitutes the hydrogen atom of the aforementioned aromatic hydrocarbonring or the aromatic hetero ring preferably has 1 to 4 carbon atoms,more preferably 1 or 2 carbon atoms, and most preferably 1 carbon atom.

The aromatic hydrocarbon group may have a substituent. For example, thehydrogen atom bonded to the aromatic ring within the aromatichydrocarbon group may be substituted with a substituent. Examples ofsubstituents include an alkyl group, an alkoxy group, a halogen atom, ahalogenated alkyl group, a hydroxyl group and an oxygen atom (═O).

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

As the structural unit (a3), a structural unit represented by generalformula (a3-1) shown below is preferable.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; P⁰represents —C(═O)—O—, —C(═O)—NR⁰— (wherein R⁰ represents a hydrogen atomor an alkyl group of 1 to 5 carbon atoms) or a single bond; and W⁰represents —COOH or a hydrocarbon group which has at least onesubstituent group selected from the group consisting of —OH, —COOH, —CN,—SO₂NH₂ and —CONH₂, provided that the hydrocarbon group may have anoxygen atom or a sulfur atom at an arbitrary position, and may besubstituted with a halogen atom.

In the formula (a3-1), as the alkyl group for R, a linear or branchedalkyl group is preferable, and specific examples include a methyl group,an ethyl group, a propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl groupand a neopentyl group.

Examples of the halogenated alkyl group for R include groups in whichpart or all of the hydrogen atoms within the aforementioned alkyl groupsof 1 to 5 carbon atoms has been substituted with a halogen atom.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom, and a fluorine atom is particularlydesirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable.

In the formula (a3-1), P⁰ represents —C(═O)—O—, —C(═O)—NR⁰— (wherein R⁰represents a hydrogen atom or an alkyl group of 1 to 5 carbon atoms) ora single bond. The alkyl group for R⁰ is the same as defined for thealkyl group for R.

In the formula (a3-1), W⁰ represents —COOH or a hydrocarbon group whichhas at least one substituent group selected from the group consisting of—OH, —COOH, —CN, —SO₂NH₂ and —CONH₂, provided that the hydrocarbon groupmay have an oxygen atom or a sulfur atom at an arbitrary position, andmay be substituted with a halogen atom.

A “hydrocarbon group which has a substituent” refers to a hydrocarbongroup in which at least part of the hydrogen atoms bonded to thehydrocarbon group is substituted with a substituent.

The hydrocarbon group for W⁰ may be either an aliphatic hydrocarbongroup, or an aromatic hydrocarbon group.

Preferable examples of the aliphatic hydrocarbon group for W⁰ includelinear or branched hydrocarbon groups of 1 to 10 carbon atoms(preferably alkylene groups) and aliphatic cyclic groups (monocyclicgroups and polycyclic groups), and are the same as explained above.

The aromatic hydrocarbon group for W⁰ is a hydrocarbon group having atleast one aromatic ring, and is the same as explained above.

W⁰ may have an oxygen atom or a sulfur atom at an arbitrary position.Here, the expression “may have an oxygen atom or a sulfur atom at anarbitrary position” means that part of the carbon atoms constituting thehydrocarbon group or the hydrocarbon group having a substituent(including the carbon atoms of the substituent part) may be substitutedwith an oxygen atom or a sulfur atom, or a hydrogen atom bonded to thehydrocarbon group may be substituted with an oxygen atom or a sulfuratom.

Further, the hydrocarbon group for W⁰ may have a hydrogen atom bondedthereto substituted with a substituent. Examples of the halogen atominclude a fluorine atom, a chlorine atom, a bromine atom and an iodineatom, and a fluorine atom is preferable.

Examples of W⁰ which has an oxygen atom (O) at an arbitrary position areshown below.

In the formulae, W⁰⁰ represents a hydrocarbon group; and R^(m)represents an alkylene group of 1 to 5 carbon atoms.

In the formulae above, W⁰⁰ represents a hydrocarbon group, and is thesame as defined for W⁰ in the aforementioned formula (a3-1). W⁰⁰ ispreferably an aliphatic hydrocarbon group, and more preferably analiphatic cyclic group (a monocyclic group or a polycyclic group).

R^(m) is preferably linear or branched, preferably an alkylene group of1 to 3 carbon atoms, and more preferably a methylene group or anethylene group.

Specific examples of preferable structural units as the structural unit(a3) include a structural unit derived from an (α-substituted) acrylateester, and structural units represented by general formulae (a3-11) to(a3-13) shown below.

Examples of the structural unit derived from an (α-substituted) acrylateester include a structural unit in which P⁰ in the aforementionedformula (a3-1) is a single bond and W⁰ is —COOH.

In the formulae, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; W⁰¹represents an aromatic hydrocarbon group which has at least onesubstituent selected from the group consisting of —OH, —COOH, —CN,—SO₂NH₂ and —CONH₂; each of P⁰² and P⁰³ independently represents—C(═O)—O—, —C(═O)—NR⁰— (wherein R⁰ represents a hydrogen atom or analkyl group of 1 to 5 carbon atoms) or a single bond; W⁰² represents acyclic hydrocarbon group having at least one substituent selected fromthe group consisting of —OH, —COOH, —CN, —SO₂NH₂ and —CONH₂, providedthat the hydrocarbon group may have an oxygen atom or a sulfur atom atan arbitrary position; and W⁰³ represents a chain-like hydrocarbon grouphaving at least one substituent selected from the group consisting of—OH, —COOH, —CN, —SO₂NH₂ and —CONH₂.

[Structural Unit Represented by General Formula (a3-11)]

In the formula (a3-11), R is the same as defined for R in theaforementioned formula (a3-1).

The aromatic hydrocarbon group for W⁰¹ is the same as defined for thearomatic hydrocarbon group for W⁰ in the aforementioned formula (a3-1).

Specific examples of structural units preferable as a structural unitrepresented by general formula (a3-11) are shown below. In the formulaeshown below, R^(α) represents a hydrogen atom, a methyl group or atrifluoromethyl group.

[Structural Unit Represented by General Formula (a3-12)]

In the formula (a3-12), R is the same as defined for R in theaforementioned formula (a3-1).

P⁰² represents —C(═O)—O— or —C(═O)—NR⁰— (wherein R⁰ represents ahydrogen atom or an alkyl group of 1 to 5 carbon atoms), and ispreferably —C(═O)—O—. The alkyl group for R⁰ is the same as defined forthe alkyl group for R.

The cyclic hydrocarbon group for W⁰² is the same as defined for thealiphatic cyclic groups (monocyclic groups and polycyclic groups) andaromatic hydrocarbon groups explained above for W⁰ in the aforementionedformula (a3-1).

W⁰² may have an oxygen atom or a sulfur atom at an arbitrary position,and is the same as defined for W⁰ in the aforementioned formula (a3-1).

Specific examples of structural units preferable as a structural unitrepresented by general formula (a3-12) are shown below. In the formulaeshown below, R^(α) represents a hydrogen atom, a methyl group or atrifluoromethyl group.

[Structural Unit Represented by General Formula (a3-13)]

In the formula (a3-13), R is the same as defined for R in theaforementioned formula (a3-1).

P⁰³ represents —C(═O)—O— or —C(═O)—NR⁰— (wherein R⁰ represents ahydrogen atom or an alkyl group of 1 to 5 carbon atoms), and ispreferably —C(═O)—O—. The alkyl group for R⁰ is the same as defined forthe alkyl group for R.

The chain-like hydrocarbon group for W⁰³ preferably has 1 to 10 carbonatoms, more preferably 1 to 5 carbon atoms, and still more preferably 1to 3 carbon atoms.

The chain-like hydrocarbon group for W⁰³ may have a substituent (a)other than —OH, —COOH, —SO₂NH₂ and —CONH₂. Examples of the substituent(a) include an alkyl group of 1 to 5 carbon atoms, an aliphatic cyclicgroup (a monocyclic group or a polycyclic group), a fluorine atom, and afluorinated alkyl group of 1 to 5 carbon atoms. The aliphatic cyclicgroup (a monocyclic group or a polycyclic group) for the substituent (a)preferably has 3 to 30 carbon atoms, more preferably 5 to 30 carbonatoms, still more preferably 5 to 20 carbon atoms, still more preferably6 to 15 carbon atoms, and most preferably 6 to 12 carbon atoms. As thealiphatic cyclic group, a group in which one or more hydrogen atoms havebeen removed from a monocycloalkane or a polycycloalkane such as abicycloalkane, tricycloalkane or tetracycloalkane can be used. Specificexamples include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane such as cyclopentane or cyclohexane; andgroups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

Further, as exemplified by a structural unit represented by generalformula (a3-13-a) shown below, the chain-like hydrocarbon group for W⁰³may have a plurality of substituents (a), and the plurality ofsubstituents (a) may be mutually bonded to form a ring.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; eachof R^(a1) and R^(a2) independently represents an alkyl group of 1 to 5carbon atoms, an aliphatic cyclic group (a monocyclic group or apolycyclic group), a fluorine atom, or a fluorinated alkyl group of 1 to5 carbon atoms, provided that R^(a1) and R^(a2) may be mutually bondedto form a ring; and q⁰ represents an integer of 1 to 4 carbon atoms.

In the formula (a3-13-a), R is the same as defined for R in theaforementioned formula (a3-1).

The aliphatic cyclic group (a monocyclic group or a polycyclic group)for R^(a1) and R^(a2) is the same as defined for the aliphatic cyclicgroup (a monocyclic group or a polycyclic group) for the substituent(a).

Further, R^(a1) and R^(a2) may be mutually bonded to form a ring. Insuch a case, a cyclic group is formed by R^(a1), R^(a2) and the carbonatom having R^(a1) and R^(a2) bonded thereto. The cyclic group may be amonocyclic group or a polycyclic group, and specific examples thereofinclude a group in which one or more hydrogen atoms have been removedfrom the monocycloalkane or polycycloalkane given as examples in theexplanation of the aliphatic cyclic group (a monocyclic group or apolycyclic group) for the substituent (a).

q⁰ is preferably 1 or 2, and more preferably 1.

Specific examples of structural units preferable as a structural unitrepresented by general formula (a3-13) are shown below. In the formulaeshown below, R^(α) represents a hydrogen atom, a methyl group or atrifluoromethyl group.

As the structural unit (a3) contained in the component (A1-1), one typeof structural unit may be used, or two or more types may be used.

In the component (A1-1), the amount of the structural unit (a3) based onthe combined total of all structural units constituting the component(A1-1) is preferably 5 to 50 mol %, more preferably 5 to 40 mol %, andstill more preferably 5 to 25 mol %.

When the amount of the structural unit (a3) is at least as large as thelower limit of the above-mentioned range, the effect of using thestructural unit (a3) (effect of improving resolution, lithographyproperties and pattern shape) can be satisfactorily achieved. On theother hand, when the amount of the structural unit (a3) is no more thanthe upper limit of the above-mentioned range, a good balance can beachieved with the other structural units.

Other Structural Units

Depending on the application, the component (A1-1) may include astructural unit other than the structural units (a5) and (a1) to (a3),as long as the effects of the present invention are not impaired.

As such a structural unit, any other structural unit which cannot beclassified as the aforementioned structural units can be used withoutany particular limitation, and any of the multitude of conventionalstructural units used within resist resins for ArF excimer lasers or KrFexcimer lasers (and particularly for ArF excimer lasers) can be used.

Examples of the other structural unit include a structural unit (a4)derived from an acrylate ester which may have the hydrogen atom bondedto the carbon atom on the α-position substituted with a substituent andcontains an acid non-dissociable aliphatic polycyclic group.

Structural Unit (a4):

The structural unit (a4) is a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent and contains an acidnon-dissociable aliphatic polycyclic group. When the component (A1-1)includes the structural unit (a4), lithography properties and etchingresistance are improved.

In the structural unit (a4), examples of this polycyclic group includethe same polycyclic groups as those described above in relation to theaforementioned structural unit (a1), and any of the multitude ofconventional polycyclic groups used within the resin component of resistcompositions for ArF excimer lasers or KrF excimer lasers (andparticularly for ArF excimer lasers) can be used.

In consideration of industrial availability and the like, at least onepolycyclic group selected from amongst a tricyclodecyl group, adamantylgroup, tetracyclododecyl group, isobornyl group, and norbornyl group isparticularly desirable. These polycyclic groups may be substituted witha linear or branched alkyl group of 1 to 5 carbon atoms.

Specific examples of the structural unit (a4) include units withstructures represented by general formulas (a4-1) to (a4-5) shown below.

In the formulae, R is the same as defined above.

When the component (A1-1) includes a structural unit (a4), as thestructural unit (a4), one type of structural unit may be used, or two ormore types may be used in combination.

When the structural unit (a4) is included in the component (A1-1), theamount of the structural unit (a4) based on the combined total of allthe structural units that constitute the component (A1-1) is preferablywithin the range from 1 to 30 mol %, and more preferably from 10 to 20mol %.

When the amount of the structural unit (a4) is at least as large as thelower limit of the above-mentioned range, the effect of using thestructural unit (a4) can be satisfactorily achieved. On the other hand,when the amount of the structural unit (a4) is no more than the upperlimit of the above-mentioned range, a good balance can be achieved withthe other structural units.

In the present invention, the component (A) contains a polymericcompound (A1) including a structural unit (a5), and the component (A1)is preferably a polymeric compound (A1-1) which exhibits increasedpolarity by the action of acid.

Specific examples of the component (A1-1) include a polymeric compoundconsisting of a repeating structure of the structural unit (a5) and thestructural unit (a1); a polymeric compound consisting of a repeatingstructure of the structural unit (a5), the structural unit (a1) and thestructural unit (a2); and a polymeric compound consisting of a repeatingstructure of the structural unit (a5), the structural unit (a1), thestructural unit (a2) and the structural unit (a3).

More specifically, preferable examples of the component (A1-1) include apolymeric compound consisting of a repeating structure of a structuralunit represented by general formula (a5-2), a structural unitrepresented by general formula (a1-0-12) and a structural unitrepresented by general formula (a2-1); a polymeric compound consistingof a repeating structure of a structural unit represented by generalformula (a5-2), a structural unit represented by general formula(a1-0-11) and a structural unit represented by general formula (a2-1); apolymeric compound consisting of a repeating structure of a structuralunit represented by general formula (a5-2), a structural unitrepresented by general formula (a1-2) and a structural unit representedby general formula (a2-1); a polymeric compound consisting of arepeating structure of a structural unit represented by general formula(a5-2), a structural unit represented by general formula (a1-0-12) and astructural unit represented by general formula (a2-0-12); a polymericcompound consisting of a repeating structure of a structural unitrepresented by general formula (a5-2), a structural unit represented bygeneral formula (a1-0-15) and a structural unit represented by generalformula (a2-0-12); a polymeric compound consisting of a repeatingstructure of a structural unit represented by general formula (a5-2), astructural unit represented by general formula (a1-0-12), a structuralunit represented by general formula (a1-0-11), a structural unitrepresented by general formula (a2-1) and a structural unit representedby general formula (a2-0-12); a polymeric compound consisting of arepeating structure of a structural unit represented by general formula(a5-2), a structural unit represented by general formula (a1-0-12), astructural unit represented by general formula (a2-0-12) and astructural unit represented by general formula (a3-12); a polymericcompound consisting of a repeating structure of a structural unitrepresented by general formula (a5-1), a structural unit represented bygeneral formula (a1-0-12) and a structural unit represented by generalformula (a2-1); and a polymeric compound consisting of a repeatingstructure of a structural unit represented by general formula (a5-2) anda structural unit represented by general formula (a1-0-12).

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component(A1-1) is not particularly limited, but is preferably 1,000 to 50,000,more preferably 1,500 to 30,000, and most preferably 2,000 to 20,000.When the weight average molecular weight is no more than the upper limitof the above-mentioned range, the resist composition exhibits asatisfactory solubility in a resist solvent. On the other hand, when theweight average molecular weight is at least as large as the lower limitof the above-mentioned range, dry etching resistance and thecross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/Mn) is not particularly limited, but ispreferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably1.0 to 2.5. Here, Mn is the number average molecular weight.

The component (A1-1) can be obtained, for example, by a conventionalradical polymerization or the like of the monomers corresponding witheach of the structural units, using a radical polymerization initiatorsuch as azobisisobutyronitrile (AIBN).

Furthermore, in the component (A1-1), by using a chain transfer agentsuch as HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introducedat the terminals of the component (A1-1). Such a copolymer havingintroduced a hydroxyalkyl group in which some of the hydrogen atoms ofthe alkyl group are substituted with fluorine atoms is effective inreducing developing defects and LER (line edge roughness: unevenness ofthe side walls of a line pattern).

As the monomers for deriving the corresponding structural units,commercially available monomers may be used, or the monomers may besynthesized by a conventional method.

In the component (A), as the component (A1), one type may be used alone,or two or more types may be used in combination.

In the component (A), the amount of the component (A1) based on thetotal weight of the component (A) is preferably 50% by weight or more,more preferably 75% by weight or more, and may even be 100% by weight.

When the amount of the component (A1) is 50% by weight or more,sensitivity, resolution and lithography properties can be more reliablyimproved.

The component (A) may contain a base component other than the component(A1) (hereafter, referred to as “component (A2)”), as long as theeffects of the present invention are not impaired. The component (A2) isnot particularly limited, and any resins and low molecular weightcompounds conventionally proposed can be used.

In the resist composition of the present invention, the amount of thecomponent (A) can be appropriately adjusted depending on the thicknessof the resist film to be formed, and the like.

<Component (B)>

The component (B) is an acid-generator component, and any of the knownacid generators used in conventional chemically amplified resistcompositions can be used.

Examples of these acid generators are numerous, and include onium saltacid generators such as iodonium salts and sulfonium salts; oximesulfonate acid generators; diazomethane acid generators such as bisalkylor bisaryl sulfonyl diazomethanes and poly(bis-sulfonyl)diazomethanes;nitrobenzylsulfonate acid generators; iminosulfonate acid generators;and disulfone acid generators.

As an onium salt acid generator, a compound represented by generalformula (b-1) or (b-2) shown below can be used.

In the formulae, R¹″ to R³″, R⁵″ and R⁶″ each independently representsan aryl group which may have a substituent, an alkyl group which mayhave a substituent or an alkenyl group which may have a substituent,provided that, in formula (b-1), two of R¹″ to R³″ may be mutuallybonded to form a ring with the sulfur atom; and R⁴″ represents an alkylgroup which may have a substituent, a halogenated alkyl group which mayhave a substituent, an aryl group which may have a substituent or analkenyl group which may have a substituent.

In formula (b-1), R¹″ to R³″ each independently represents an aryl groupwhich may have a substituent or an alkyl group which may have asubstituent. Two of R¹″ to R³″ may be mutually bonded to form a ringwith the sulfur atom.

In terms of improvement in lithography properties and resist patternshape, it is preferable that at least one of R¹″ to R³″ is an arylgroup, it is more preferable that two or more of R¹″ to R³″ are arylgroups, and it is most preferable that all of R¹″ to R³″ are arylgroups.

Examples of the aryl group for R¹″ to R³″ include an unsubstituted arylgroup of 6 to 20 carbon atoms; a substituted aryl group in which part orall of the hydrogen atoms of the aforementioned unsubstituted aryl grouphas been substituted with an alkyl group, an alkoxy group, a halogenatom, a hydroxy group, an oxo group (═O), an aryl group, analkoxyalkyloxy group, an alkoxycarbonylalkyloxy group, —C(═O)—O—R⁶′,—O—C(═O)—R⁷′ or —O—R⁸′. Each of R⁶′, R⁷′ and R⁸′ independentlyrepresents a linear or branched saturated hydrocarbon group of 1 to 25atoms, a cyclic saturated hydrocarbon group of 3 to 20 carbon atoms or alinear or branched, aliphatic unsaturated hydrocarbon group of 2 to 5carbon atoms.

The unsubstituted aryl group for R¹″ to R³″ is preferably an aryl grouphaving 6 to 10 carbon atoms because it can be synthesized at a low cost.Specific examples thereof include a phenyl group and a naphthyl group.

The alkyl group as the substituent for the substituted aryl grouprepresented by R¹″ to R³″ is preferably an alkyl group having 1 to 5carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group, or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent for the substituted aryl group ispreferably an alkoxy group having 1 to 5 carbon atoms, and a methoxygroup, an ethoxy group, an n-propoxy group, an iso-propoxy group, ann-butoxy group or a tert-butoxy group is particularly desirable.

The halogen atom as the substituent for the substituted aryl group ispreferably a fluorine atom.

As the aryl group as the substituent for the substituted aryl group, thesame aryl groups as those described above for R¹″ to R³″ can bementioned, and an aryl group of 6 to 20 carbon atoms is preferable, anaryl group of 6 to 10 carbon atoms is more preferable, and a phenylgroup or a naphthyl group is still more preferable.

Examples of alkoxyalkyloxy groups as the substituent for the substitutedaryl group include groups represented by a general formula shown below:—O—C(R⁴⁷)(R⁴⁸)—O—R⁴⁹

In the formula, R⁴⁷ and R⁴⁸ each independently represents a hydrogenatom or a linear or branched alkyl group; and R⁴⁹ represents an alkylgroup.

The alkyl group for R⁴⁷ and R⁴⁸ preferably has 1 to 5 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable.

It is preferable that at least one of R⁴⁷ and R⁴⁸ be a hydrogen atom. Itis particularly desirable that at least one of R⁴⁷ and R⁴⁸ be a hydrogenatom, and the other be a hydrogen atom or a methyl group.

The alkyl group for R⁴⁹ preferably has 1 to 15 carbon atoms, and may belinear, branched or cyclic.

The linear or branched alkyl group for R⁴⁹ preferably has 1 to 5 carbonatoms. Examples thereof include a methyl group, an ethyl group, a propylgroup, an n-butyl group and a tert-butyl group.

The cyclic alkyl group for R⁴⁹ preferably has 4 to 15 carbon atoms, morepreferably 4 to 12, and most preferably 5 to 10. Specific examplesthereof include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane or a polycycloalkane such as abicycloalkane, tricycloalkane or tetracycloalkane, and which may or maynot be substituted with an alkyl group of 1 to 5 carbon atoms, afluorine atom or a fluorinated alkyl group. Examples of themonocycloalkane include cyclopentane and cyclohexane. Examples ofpolycycloalkanes include adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

Examples of the alkoxycarbonylalkyloxy group as the substituent for thesubstituted aryl group include groups represented by a general formulashown below:—O—R⁵⁰—C(═O)—O—R⁵⁶

In the formula, R⁵⁰ represents a linear or branched alkylene group, andR⁵⁶ represents a tertiary alkyl group.

The linear or branched alkylene group for R⁵⁰ preferably has 1 to 5carbon atoms, and examples thereof include a methylene group, anethylene group, a trimethylene group, a tetramethylene group and a1,1-dimethylethylene group.

Examples of the tertiary alkyl group for R⁵⁶ include a2-methyl-2-adamantyl group, a 2-ethyl-2-adamantyl group, a1-methyl-1-cyclopentyl group, a 1-ethyl-1-cyclopentyl group, a1-methyl-1-cyclohexyl group, a 1-ethyl-1-cyclohexyl group, a1-(1-adamantyl)-1-methylethyl group, a 1-(1-adamantyl)-1-methylpropylgroup, a 1-(1-adamantyl)-1-methylbutyl group, a1-(1-adamantyl)-1-methylpentyl group, a 1-(1-cyclopentyl)-1-methylethylgroup, a 1-(1-cyclopentyl)-1-methylpropyl group, a1-(1-cyclopentyl)-1-methylbutyl group, a1-(1-cyclopentyl)-1-methylpentyl group, a 1-(1-cyclohexyl)-1-methylethylgroup, a 1-(1-cyclohexyl)-1-methylpropyl group, a1-(1-cyclohexyl)-1-methylbutyl group, a 1-(1-cyclohexyl)-1-methylpentylgroup, a tert-butyl group, a tert-pentyl group and a tert-hexyl group.

Further, a group in which R⁵⁶ in the group represented by theaforementioned general formula: —O—R⁵⁰—C(═O)—O—R⁵⁶ has been substitutedwith R⁵⁶′ can also be mentioned. R⁵⁶′ represents a hydrogen atom, analkyl group, a fluorinated alkyl group or an aliphatic cyclic groupwhich may contain a hetero atom.

The alkyl group for R⁵⁶′ is the same as defined for the alkyl group forthe aforementioned R⁴⁹.

Examples of the fluorinated alkyl group for R⁵⁶′ include groups in whichpart or all of the hydrogen atoms within the alkyl group for R⁴⁹ hasbeen substituted with a fluorine atom.

Examples of the aliphatic cyclic group for R⁵⁶′ which may contain ahetero atom include an aliphatic cyclic group which does not contain ahetero atom, an alipahtic cyclic group containing a hetero atom in thering structure, and an aliphatic cyclic group in which a hydrogen atomhas been substituted with a hetero atom.

As an aliphatic cyclic group for R⁵⁶′ which does not contain a heteroatom, a group in which one or more hydrogen atoms have been removed froma monocycloalkane or a polycycloalkane such as a bicycloalkane, atricycloalkane or a tetracycloalkane can be mentioned. Examples of themonocycloalkane include cyclopentane and cyclohexane. Examples ofpolycycloalkanes include adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

Specific examples of the aliphatic cyclic group for R⁵⁶′ containing ahetero atom in the ring structure include groups represented by formulas(L1) to (L6) and (S1) to (S4) described later.

As the aliphatic cyclic group for R⁵⁶′ in which a hydrogen atom has beensubstituted with a hetero atom, an aliphatic cyclic group in which ahydrogen atom has been substituted with an oxygen atom (═O) can bementioned.

In formulae —C(═O)—O—R⁶′, —O—C(═O)—R⁷′ and —O—R⁸′, R⁶′, R⁷′ and R⁸′ eachindependently represents a linear or branched saturated hydrocarbongroup of 1 to 25 atoms, a cyclic saturated hydrocarbon group of 3 to 20carbon atoms or a linear or branched, aliphatic unsaturated hydrocarbongroup of 2 to 5 carbon atoms.

The linear or branched, saturated hydrocarbon group preferably has 1 to25 carbon atoms, more preferably 1 to 15, and still more preferably 4 to10.

Examples of the linear, saturated hydrocarbon group include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a nonyl group and a decylgroup.

Examples of the branched, saturated hydrocarbon group include a1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a2-methylpentyl group, a 3-methylpentyl group and a 4-methylpentyl group,but excluding tertiary alkyl groups. The linear or branched, saturatedhydrocarbon group may have a substituent.

Examples of the substituent include an alkoxy group, a halogen atom, ahalogenated alkyl group, a hydroxyl group, an oxygen atom (═O), a cyanogroup and a carboxy group.

The alkoxy group as the substituent for the linear or branched saturatedhydrocarbon group is preferably an alkoxy group having 1 to 5 carbonatoms, more preferably a methoxy group, an ethoxy group, an n-propoxygroup, an iso-propoxy group, an n-butoxy group or a tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the linear orbranched, saturated alkyl group include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

Example of the halogenated alkyl group as the substituent for the linearor branched, saturated hydrocarbon group includes a group in which partor all of the hydrogen atoms within the aforementioned linear orbranched, saturated hydrocarbon group have been substituted with theaforementioned halogen atoms.

The cyclic saturated hydrocarbon group of 3 to 20 carbon atoms for R⁶′,R⁷′ and R⁸′ may be either a polycyclic group or a monocyclic group, andexamples thereof include groups in which one hydrogen atom has beenremoved from a monocycloalkane, and groups in which one hydrogen atomhas been removed from a polycycloalkane (e.g., a bicycloalkane, atricycloalkane or a tetracycloalkane). More specific examples includegroups in which one hydrogen atom has been removed from amonocycloalkane such as cyclopentane, cyclohexane, cycloheptane orcyclooctane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

The cyclic, saturated hydrocarbon group may have a substituent. Forexample, part of the carbon atoms constituting the ring within thecyclic alkyl group may be substituted with a hetero atom, or a hydrogenatom bonded to the ring within the cyclic alkyl group may be substitutedwith a substituent.

In the former example, a heterocycloalkane in which part of the carbonatoms constituting the ring within the aforementioned monocycloalkane orpolycycloalkane has been substituted with a hetero atom such as anoxygen atom, a sulfur atom or a nitrogen atom, and one hydrogen atom hasbeen removed therefrom, can be used. Further, the ring may contain anester bond (—C(═O)—O—). More specific examples include alactone-containing monocyclic group, such as a group in which onehydrogen atom has been removed from γ-butyrolactone; and alactone-containing polycyclic group, such as a group in which onehydrogen atom has been removed from a bicycloalkane, tricycloalkane ortetracycloalkane containing a lactone ring.

In the latter example, as the substituent, the same substituent groupsas those for the aforementioned linear or branched alkyl group, or alower alkyl group can be used.

Alternatively, R⁶′, R⁷′ and R⁸′ may be a combination of a linear orbranched alkyl group and a cyclic group.

Examples of the combination of a linear or branched alkyl group with acyclic alkyl group include groups in which a cyclic alkyl group as asubstituent is bonded to a linear or branched alkyl group, and groups inwhich a linear or branched alkyl group as a substituent is bonded to acyclic alkyl group.

Examples of the linear aliphatic unsaturated hydrocarbon group for R⁶′,R⁷′ and R⁸′ include a vinyl group, a propenyl group (an allyl group) anda butynyl group.

Examples of the branched aliphatic unsaturated hydrocarbon group forR⁶′, R⁷′ and R⁸′ include a 1-methylpropenyl group and a 2-methylpropenylgroup.

The aforementioned linear or branched, aliphatic unsaturated hydrocarbongroup may have a substituent. Examples of substituents include the samesubstituents as those which the aforementioned linear or branched alkylgroup may have.

Among the aforementioned examples, as R⁷′ and R⁸′, in terms ofimprovement in lithography properties and shape of the resist pattern, alinear or branched, saturated hydrocarbon group of 1 to 15 carbon atomsor a cyclic saturated hydrocarbon group of 3 to 20 carbon atoms ispreferable.

The aryl group for each of R¹″ to R³″ is preferably a phenyl group or anaphthyl group.

Examples of the alkyl group for R¹″ to R³″ include linear, branched orcyclic alkyl groups of 1 to 10 carbon atoms. Among these, alkyl groupsof 1 to 5 carbon atoms are preferable as the resolution becomesexcellent. Specific examples thereof include a methyl group, an ethylgroup, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an n-pentyl group, a cyclopentyl group, a hexyl group, acyclohexyl group, a nonyl group, and a decyl group, and a methyl groupis most preferable because it is excellent in resolution and can besynthesized at a low cost.

The alkenyl group for R¹″ to R³″ preferably has 2 to 10 carbon atoms,more preferably 2 to 5, and still more preferably 2 to 4. Specificexamples thereof include a vinyl group, a propenyl group (an allylgroup), a butynyl group, a 1-methylpropenyl group and a 2-methylpropenylgroup.

When two of R¹″ to R³″ are bonded to each other to form a ring with thesulfur atom, it is preferable that the two of to R³″ form a 3 to10-membered ring including the sulfur atom, and it is particularlydesirable that the two of R¹″ to R³″ form a 5 to 7-membered ringincluding the sulfur atom.

When two of R¹″ to R³″ are bonded to each other to form a ring with thesulfur atom, the remaining one of R¹″ to R³″ is preferably an arylgroup. As examples of the aryl group, the same as the above-mentionedaryl groups for R¹″ to R³″ can be given.

Specific examples of cation moiety of the compound represented bygeneral formula (b-1) include triphenylsulfonium,(3,5-dimethylphenyl)diphenylsulfonium,(4-(2-adamantoxymethyloxy)-3,5-dimethylphenyl)diphenylsulfonium,(4-(2-adamantoxymethyloxy)phenyl)diphenylsulfonium,(4-(tert-butoxycarbonylmethyloxy)phenyl)diphenylsulfonium,(4-(tert-butoxycarbonylmethyloxy)-3,5-dimethylphenyl)diphenylsulfonium,(4-(2-methyl-2-adamantyloxycarbonylmethyloxy)phenyl)diphenylsulfonium,(4-(2-methyl-2-adamantyloxycarbonylmethyloxy)-3,5-dimethylphenyl)diphenylsulfonium, tri(4-methylphenyl)sulfonium,dimethyl(4-hydroxynaphthyl)sulfonium, monophenyldimethylsulfonium,diphenylmonomethylsulfonium, (4-methylphenyl)diphenylsulfonium,(4-methoxyphenyl)diphenylsulfonium, tri(4-tert-butyl)phenylsulfonium,diphenyl(1-(4-methoxy)naphthyl)sulfonium, di(1-naphthyl)phenylsulfonium,1-phenyltetrahydrothiophenium, 1-(4-methylphenyl)tetrahydrothiophenium,1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiophenium,1-(4-methoxynaphthalene-1-yl)tetrahydrothiophenium,1-(4-ethoxynaphthalene-1-yl)tetrahydrothiophenium,1-(4-n-butoxynaphthalene-1-yl)tetrahydrothiophenium,1-phenyltetrahydrothiopyranium,1-(4-hydroxyphenyl)tetrahydrothiopyranium,1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopyranium and1-(4-methylphenyl)tetrahydrothiopyranium.

Preferable examples of the cation moiety of the compound represented bythe aforementioned formula (b-1) are shown below.

In the formula, g1 represents a recurring number, and is an integer of 1to 5.

In the formula, g2 and g3 represent recurring numbers, wherein g2 is aninteger of 0 to 20, and g3 is an integer of 0 to 20.

In formulas (b-1) and (b-2), R⁴″ represents an alkyl group, ahalogenated alkyl group, an aryl group or an alkenyl group which mayhave a substituent.

The alkyl group for R⁴″ may be any of linear, branched or cyclic.

The linear or branched alkyl group preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbonatoms.

The cyclic alkyl group preferably has 4 to 15 carbon atoms, morepreferably 4 to 10 carbon atoms, and most preferably 6 to 10 carbonatoms.

As an example of the halogenated alkyl group for R⁴″, a group in whichpart of or all of the hydrogen atoms of the aforementioned linear,branched or cyclic alkyl group have been substituted with halogen atomscan be given. Examples of the aforementioned halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom, and afluorine atom is preferable.

In the halogenated alkyl group, the percentage of the number of halogenatoms based on the total number of halogen atoms and hydrogen atoms(halogenation ratio (%)) is preferably 10 to 100%, more preferably 50 to100%, and most preferably 100%. Higher halogenation ratio is preferablebecause the acid strength increases.

The aryl group for R⁴″ is preferably an aryl group of 6 to 20 carbonatoms.

The alkenyl group for R⁴″ is preferably an alkenyl group of 2 to 10carbon atoms.

With respect to R⁴″, the expression “may have a substituent” means thatpart of or all of the hydrogen atoms within the aforementioned linear,branched or cyclic alkyl group, halogenated alkyl group, aryl group oralkenyl group may be substituted with substituents (atoms other thanhydrogen atoms, or groups).

R⁴″ may have one substituent, or two or more substituents.

Examples of the substituent include a halogen atom, a hetero atom, analkyl group, a hydroxy group, and a group represented by the formulaX³-Q¹- (in the formula, Q¹ represents a divalent linking groupcontaining an oxygen atom; and X³ represents a hydrocarbon group of 3 to30 carbon atoms which may have a substituent).

Examples of halogen atoms and alkyl groups as substituents for R⁴″include the same halogen atoms and alkyl groups as those described abovewith respect to the halogenated alkyl group for R⁴″.

Examples of hetero atoms include an oxygen atom, a nitrogen atom, and asulfur atom.

In the group represented by formula X³-Q¹-, Q¹ represents a divalentlinking group containing an oxygen atom.

Q¹ may contain an atom other than oxygen. Examples of atoms other thanoxygen include a carbon atom, a hydrogen atom, a sulfur atom and anitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an amido bond(—C(═O)—NH—), a carbonyl group (—C(═O)—) and a carbonate bond(—O—C(═O)—O—); and combinations of the aforementioned non-hydrocarbon,hetero atom-containing linking groups with an alkylene group.

Specific examples of the combinations of the aforementionednon-hydrocarbon, hetero atom-containing linking groups and an alkylenegroup include —R⁹¹—O—, —R⁹²—O—C(═O)—, —C(═O)—O—R⁹³—O—C(═O)— (in theformulas, each of R⁹¹ to R⁹³ independently represents an alkylenegroup).

The alkylene group for R⁹¹ to R⁹³ is preferably a linear or branchedalkylene group, and preferably has 1 to 12 carbon atoms, more preferably1 to 5, and most preferably 1 to 3.

Specific examples of alkylene groups include a methylene group [—CH₂—];alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—,—C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and —C(CH₂CH₃)₂—; an ethylenegroup [—CH₂CH₂—]; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—; a trimethylene group(n-propylene group) [—CH₂CH₂CH₂—]; alkyltrimethylene groups such as—CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; a tetramethylene group[—CH₂CH₂CH₂CH₂—]; alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—and —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group [—CH₂CH₂CH₂CH₂CH₂—].

Q¹ is preferably a divalent linking group containing an ester linkage orether linkage, and more preferably a group of —R⁹¹—O—, —R⁹²—O—C(═O)— or—C(═O)—O—R⁹³—O—C(═O)—.

In the group represented by the formula X³-Q¹-, the hydrocarbon groupfor X³ may be either an aromatic hydrocarbon group or an aliphatichydrocarbon group.

The aromatic hydrocarbon group is a hydrocarbon group having an aromaticring. The aromatic hydrocarbon ring preferably has 3 to 30 carbon atoms,more preferably 5 to 30, still more preferably 5 to 20, still morepreferably 6 to 15, and most preferably 6 to 12. Here, the number ofcarbon atoms within a substituent(s) is not included in the number ofcarbon atoms of the aromatic hydrocarbon group.

Specific examples of aromatic hydrocarbon groups include an aryl groupwhich is an aromatic hydrocarbon ring having one hydrogen atom removedtherefrom, such as a phenyl group, a biphenyl group, a fluorenyl group,a naphthyl group, an anthryl group or a phenanthryl group; and analkylaryl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group. The alkyl chain within the arylalkylgroup preferably has 1 to 4 carbon atom, more preferably 1 or 2, andmost preferably 1.

The aromatic hydrocarbon group may have a substituent. For example, partof the carbon atoms constituting the aromatic ring within the aromatichydrocarbon group may be substituted with a hetero atom, or a hydrogenatom bonded to the aromatic ring within the aromatic hydrocarbon groupmay be substituted with a substituent.

In the former example, a heteroaryl group in which part of the carbonatoms constituting the ring within the aforementioned aryl group hasbeen substituted with a hetero atom such as an oxygen atom, a sulfuratom or a nitrogen atom, and a heteroarylalkyl group in which part ofthe carbon atoms constituting the aromatic hydrocarbon ring within theaforementioned arylalkyl group has been substituted with theaforementioned heteroatom can be used.

In the latter example, as the substituent for the aromatic hydrocarbongroup, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) or the like can beused.

The alkyl group as the substituent for the aromatic hydrocarbon group ispreferably an alkyl group of 1 to 5 carbon atoms, and a methyl group, anethyl group, a propyl group, an n-butyl group or a tert-butyl group isparticularly desirable.

The alkoxy group as the substituent for the aromatic hydrocarbon groupis preferably an alkoxy group having 1 to 5 carbon atoms, morepreferably a methoxy group, ethoxy group, n-propoxy group, iso-propoxygroup, n-butoxy group or tert-butoxy group, and most preferably amethoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Example of the halogenated alkyl group as the substituent for thearomatic hydrocarbon group includes a group in which part or all of thehydrogen atoms within the aforementioned alkyl group have beensubstituted with the aforementioned halogen atoms.

The aliphatic hydrocarbon group for X³ may be either a saturatedaliphatic hydrocarbon group, or an unsaturated aliphatic hydrocarbongroup. Further, the aliphatic hydrocarbon group may be linear, branchedor cyclic.

In the aliphatic hydrocarbon group for X³, part of the carbon atomsconstituting the aliphatic hydrocarbon group may be substituted with asubstituent group containing a hetero atom, or part or all of thehydrogen atoms constituting the aliphatic hydrocarbon group may besubstituted with a substituent group containing a hetero atom.

As the “hetero atom” for X³, there is no particular limitation as longas it is an atom other than carbon and hydrogen.

Examples of the halogen atom include a fluorine atom, a chlorine atom,an iodine atom and a bromine atom.

The substituent group containing a hetero atom may consist of a heteroatom, or may be a group containing a group or atom other than a heteroatom.

Specific examples of the substituent group for substituting part of thecarbon atoms include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—,—NH— (the H may be replaced with a substituent such as an alkyl group oran acyl group), —S—, —S(═O)₂— and —S(═O)₂—O—. When the aliphatichydrocarbon group is cyclic, the aliphatic hydrocarbon group may containany of these substituent groups in the ring structure.

Examples of the substituent group for substituting part or all of thehydrogen atoms include an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) and a cyano group.

The aforementioned alkoxy group is preferably an alkoxy group having 1to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the aforementioned halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

Example of the aforementioned halogenated alkyl group includes a groupin which part or all of the hydrogen atoms within an alkyl group of 1 to5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

As the aliphatic hydrocarbon group, a linear or branched saturatedhydrocarbon group, a linear or branched monovalent unsaturatedhydrocarbon group, or a cyclic aliphatic hydrocarbon group (aliphaticcyclic group) is preferable.

The linear saturated hydrocarbon group (alkyl group) preferably has 1 to20 carbon atoms, more preferably 1 to 15, and most preferably 1 to 10.Specific examples include a methyl group, an ethyl group, a propylgroup, a butyl group, a pentyl group, a hexyl group, a heptyl group, anoctyl group, a nonyl group, a decyl group, an undecyl group, a dodecylgroup, a tridecyl group, an isotridecyl group, a tetradecyl group, apentadecyl group, a hexadecyl group, an isohexadecyl group, a heptadecylgroup, an octadecyl group, a nonadecyl group, an icosyl group, ahenicosyl group and a docosyl group.

The branched saturated hydrocarbon group (alkyl group) preferably has 3to 20 carbon atoms, more preferably 3 to 15, and most preferably 3 to10. Specific examples include a 1-methylethyl group, a 1-methylpropylgroup, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutylgroup, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutylgroup, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentylgroup and a 4-methylpentyl group.

The unsaturated hydrocarbon group preferably has 2 to 10 carbon atoms,more preferably 2 to 5, still more preferably 2 to 4, and mostpreferably 3. Examples of linear monovalent unsaturated hydrocarbongroups include a vinyl group, a propenyl group (an allyl group) and abutynyl group. Examples of branched monovalent unsaturated hydrocarbongroups include a 1-methylpropenyl group and a 2-methylpropenyl group.

Among the above-mentioned examples, as the unsaturated hydrocarbongroup, a propenyl group is particularly desirable.

The aliphatic cyclic group may be either a monocyclic group or apolycyclic group. The aliphatic cyclic group preferably has 3 to 30carbon atoms, more preferably 5 to 30, still more preferably 5 to 20,still more preferably 6 to 15, and most preferably 6 to 12.

As the aliphatic cyclic group, a group in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane can be used.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane such as cyclopentane orcyclohexane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

When the aliphatic cyclic group does not contain a heteroatom-containing substituent group in the ring structure thereof, thealiphatic cyclic group is preferably a polycyclic group, more preferablya group in which one or more hydrogen atoms have been removed from apolycycloalkane, and a group in which one or more hydrogen atoms havebeen removed from adamantane is particularly desirable.

When the aliphatic cyclic group contains a hetero atom-containingsubstituent group in the ring structure thereof, the heteroatom-containing substituent group is preferably —O—, —C(═O)—O—, —S—,—S(═O)₂— or —S(═O)₂—O—. Specific examples of such aliphatic cyclicgroups include groups represented by formulas (L1) to (L6) and (S1) to(S4) shown below.

In the formula, Q″ represents an alkylene group of 1 to 5 carbon atoms,—O—, —S—, —O—R⁹⁴— or —S—R⁹⁵— (wherein each of R⁹⁴ and R⁹⁵ independentlyrepresents an alkylene group of 1 to 5 carbon atoms); and m represents 0or 1.

As the alkylene group for Q″, R⁹⁴ and R⁹⁵, the same alkylene groups asthose described above for R⁹¹ to R⁹³ can be used.

In these aliphatic cyclic groups, part of the hydrogen atoms bonded tothe carbon atoms constituting the ring structure may be substituted witha substituent. Examples of substituents include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and an oxygen atom (═O).

As the alkyl group, an alkyl group of 1 to 5 carbon atoms is preferable,and a methyl group, an ethyl group, a propyl group, an n-butyl group ora tert-butyl group is particularly desirable.

As the alkoxy group and the halogen atom, the same groups as thesubstituent groups for substituting part or all of the hydrogen atomscan be used.

In the present invention, as X³, a cyclic group which may have asubstituent is preferable. The cyclic group may be either an aromatichydrocarbon group which may have a substituent, or an aliphatic cyclicgroup which may have a substituent, and an aliphatic cyclic group whichmay have a substituent is preferable.

As the aromatic hydrocarbon group, a naphthyl group which may have asubstituent, or a phenyl group which may have a substituent ispreferable.

As the aliphatic cyclic group which may have a substituent, an aliphaticpolycyclic group which may have a substituent is preferable. As thealiphatic polycyclic group, the aforementioned group in which one ormore hydrogen atoms have been removed from a polycycloalkane, and agroup represented by any one of the aforementioned formulae (L2) to(L6), (S3) and (S4) is preferable.

In the present invention, R⁴″ preferably has X³-Q¹- as a substituent. Insuch a case, R⁴″ is preferably a group represented by the formulaX³-Q¹-Y¹⁰—(in the formula, Q¹ and X³ are the same as defined above; andY¹⁰ represents an alkylene group of 1 to 4 carbon atoms which may have asubstituent, or a fluorinated alkylene group of 1 to 4 carbon atomswhich may have a substituent).

In the group represented by the formula: X³-Q¹-Y¹⁰—, examples of thealkylene group for Y¹⁰ include the same alkylene groups as thosedescribed above for Q¹ which has 1 to 4 carbon atoms.

As the fluorinated alkylene group, the aforementioned alkylene group inwhich part or all of the hydrogen atoms has been substituted withfluorine atoms can be used.

Specific examples of Y¹⁰ include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—,—CF(CF₃)CF₂—, —CF(CF₂CF₃)—, —C(CF₃)₂—, —CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—,—CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—, —C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—,—CF(CF₂CF₂CF₃)—, —C(CF₃)(CF₂CF₃)—; —CHF—, —CH₂CF₂—, —CH₂CH₂CF₂—,—CH₂CF₂CF₂—, —CH(CF₃)CH₂—, —CH(CF₂CF₃)—, —C(CH₃)(CF₃)—, —CH₂CH₂CH₂CF₂—,—CH₂CH₂CF₂CF₂—, —CH(CF₃)CH₂CH₂—, —CH₂CH(CF₃)CH₂—, —CH(CF₃)CH(CF₃)—,—C(CF₃)₂CH₂—; —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —CH₂CH₂CH₂CH₂—, —CH(CH₃)CH₂CH₂—, —CH₂CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, —CH(CH₂CH₂CH₃)—, and—C(CH₃)(CH₂CH₃)—.

Y¹⁰ is preferably a fluorinated alkylene group, and particularlypreferably a fluorinated alkylene group in which the carbon atom bondedto the adjacent sulfur atom is fluorinated. Examples of such fluorinatedalkylene groups include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—, —CF(CF₃)CF₂—,—CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—, —CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—,—C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—; —CH₂CF₂—, —CH₂CH₂CF₂—, —CH₂CF₂CF₂—;—CH₂CH₂CH₂CF₂—, —CH₂CH₂CF₂CF₂—, and —CH₂CF₂CF₂CF₂—.

Of these, —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂— or CH₂CF₂CF₂— is preferable,—CF₂—, —CF₂CF₂— or —CF₂CF₂CF₂— is more preferable, and —CF₂— isparticularly desirable.

The alkylene group or fluorinated alkylene group may have a substituent.The alkylene group or fluorinated alkylene group “has a substituent”means that part or all of the hydrogen atoms or fluorine atoms in thealkylene group or fluorinated alkylene group has been substituted withgroups other than hydrogen atoms and fluorine atoms.

Examples of substituents which the alkylene group or fluorinatedalkylene group may have include an alkyl group of 1 to 4 carbon atoms,an alkoxy group of 1 to 4 carbon atoms, and a hydroxyl group.

In formula (b-2), R⁵″ and R⁶″ each independently represents an arylgroup which may have a substituent or an alkyl group which may have asubstituent.

In terms of improvement in lithography properties and resist patternshape, it is preferable that at least one of R⁵″ and R⁶″ is an arylgroup, and it is more preferable that both R⁵″ and R⁶″ represent an arylgroup.

As the aryl group for R⁵″ and R⁶″, the same aryl groups as thosedescribed above for R¹″ to R³″ can be used.

As the alkyl group for R⁵″ and R⁶″, the same alkyl groups as thosedescribed above for R¹″ to R³″ can be used.

As the alkenyl group for R⁵″ and R⁶″, the same as the alkenyl groups forR¹″ to R³″ can be used.

It is particularly desirable that both of R⁵″ and R⁶″ represents aphenyl group.

Specific examples of the cation moiety of the compound represented bygeneral formula (b-2) include diphenyliodonium andbis(4-tert-butylphenyl)iodonium.

As R⁴″ in formula (b-2), the same groups as those mentioned above forR⁴″ in formula (b-1) can be used.

Specific examples of suitable onium salt acid generators represented byformula (b-1) or (b-2) include diphenyliodoniumtrifluoromethanesulfonate or nonafluorobutanesulfonate;bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate ornonafluorobutanesulfonate; triphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-methylphenyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;dimethyl(4-hydroxynaphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;monophenyldimethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenylmonomethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-tert-butyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenyl(1-(4-methoxy)naphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;di(1-naphthyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-phenyltetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(4-methylphenyl)tetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-methoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-ethoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-n-butoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-phenyltetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-(4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; and 1-(4-methylphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate.

Furthermore, onium salts in which the anion moiety of these onium saltsare replaced by an anion moiety represented by any one of formulae (b1)to (b9) shown below can be used. Among these, it is more preferable touse onium salts in which the anion moiety of these onium salts arereplaced by an anion moiety represented by any one of formulae (b3) to(b6) and (b9) shown below, and it is particularly desirable to use anonium salt in which the anion moiety has been replaced by an anionmoiety represented by any formula (b9) shown below.

These anions have a structure similar to the anion moieties of thecomponent (D1) described later. Therefore, it is presumed that, by usingan onium salt in which the anion moiety is replaced by any of theseanions, the effects of the present invention can be improved.

In the formulae, q1 and q2 each independently represents an integer of 1to 5; q3 represents an integer of 1 to 12; t3 represents an integer of 1to 3; r1 and r2 each independently represents an integer of 0 to 3; irepresents an integer of 1 to 20; R⁷ represents a substituent; m1 to m6each independently represents 0 or 1; v0 to v6 each independentlyrepresents an integer of 0 to 3; w1 to w6 each independently representsan integer of 0 to 3; and Q″ is the same as defined above.

As the substituent for R⁷, the same groups as those which theaforementioned aliphatic hydrocarbon group or aromatic hydrocarbon groupfor X³ may have as a substituent can be used.

If there are two or more of the R⁷ group, as indicated by the values r1,r2, and w1 to w6, then the two or more of the R⁷ groups may be the sameor different from each other.

Further, onium salt-based acid generators in which the anion moiety ingeneral formula (b-1) or (b-2) is replaced by an anion represented bygeneral formula (b-3) or (b-4) shown below (the cation moiety is thesame as (b-1) or (b-2)) may be used.

In the formulas, X″ represents an alkylene group of 2 to 6 carbon atomsin which at least one hydrogen atom has been substituted with a fluorineatom; and each of Y″ and Z″ independently represents an alkyl group of 1to 10 carbon atoms in which at least one hydrogen atom has beensubstituted with a fluorine atom.

X″ represents a linear or branched alkylene group in which at least onehydrogen atom has been substituted with a fluorine atom, and thealkylene group has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms,and most preferably 3 carbon atoms.

Each of Y″ and Z″ independently represents a linear or branched alkylgroup in which at least one hydrogen atom has been substituted with afluorine atom, and the alkyl group has 1 to 10 carbon atoms, preferably1 to 7 carbon atoms, and most preferably 1 to 3 carbon atoms.

The smaller the number of carbon atoms of the alkylene group for X″ orthose of the alkyl group for Y″ and Z″ within the above-mentioned rangeof the number of carbon atoms, the more the solubility in a resistsolvent is improved.

Further, in the alkylene group for X″ or the alkyl group for Y″ and Z″,it is preferable that the number of hydrogen atoms substituted withfluorine atoms is as large as possible because the acid strengthincreases and the transparency to high energy radiation of 200 nm orless or electron beam is improved.

The fluorination ratio of the alkylene group or alkyl group ispreferably from 70 to 100%, more preferably from 90 to 100%, and it isparticularly desirable that the alkylene group or alkyl group be aperfluoroalkylene group or perfluoroalkyl group in which all hydrogenatoms are substituted with fluorine atoms.

Furthermore, as an onium salt-based acid generator, a sulfonium salthaving a cation represented by general formula (b-5) or (b-6) shownbelow as the cation moiety may be used.

In formulas (b-5) and (b-6) above, each of R⁸¹ to R⁸⁶ independentlyrepresents an alkyl group, an acetyl group, an alkoxy group, a carboxygroup, a hydroxyl group or a hydroxyalkyl group; each of n₁ to n₅independently represents an integer of 0 to 3; and n₆ represents aninteger of 0 to 2.

With respect to R⁸¹ to R⁸⁶, the alkyl group is preferably an alkyl groupof 1 to 5 carbon atoms, more preferably a linear or branched alkylgroup, and most preferably a methyl group, ethyl group, propyl group,isopropyl group, n-butyl group or tert butyl group.

The alkoxy group is preferably an alkoxy group of 1 to 5 carbon atoms,more preferably a linear or branched alkoxy group, and most preferably amethoxy group or ethoxy group.

The hydroxyalkyl group is preferably the aforementioned alkyl group inwhich one or more hydrogen atoms have been substituted with hydroxygroups, and examples thereof include a hydroxymethyl group, ahydroxyethyl group and a hydroxypropyl group.

If there are two or more of an individual R⁸¹ to R⁸⁶ group, as indicatedby the corresponding value of n₁ to n₆, then the two or more of theindividual R⁸¹ to R⁸⁶ group may be the same or different from eachother.

n₁ is preferably 0 to 2, more preferably 0 or 1, and still morepreferably 0.

It is preferable that n₂ and n₃ each independently represent 0 or 1, andmore preferably 0.

n₄ is preferably 0 to 2, and more preferably 0 or 1.

n₅ is preferably 0 or 1, and more preferably 0.

n₆ is preferably 0 or 1, and more preferably 1.

Preferable examples of the cation represented by formula (b-5) or (b-6)are shown below.

Furthermore, a sulfonium salt having a cation represented by generalformula (b-7) or (b-8) shown below as the cation moiety may be used.

In formulas (b-7) and (b-8) shown below, each of R⁹ and R¹⁰independently represents a phenyl group or naphthyl group which may havea substituent, an alkyl group of 1 to 5 carbon atoms, an alkoxy group ora hydroxyl group. Examples of the substituent are the same as thesubstituents described above in relation to the substituted aryl groupfor R¹″ to R³″ (i.e., an alkyl group, an alkoxy group, an alkoxyalkyloxygroup, an alkoxycarbonylalkyloxy group, a halogen atom, a hydroxy group,an oxo group (═O), an aryl group, —C(═O)—O—R⁶′, —O—C(═O)—R⁷′, —O—R⁸′, agroup in which R⁵⁶′ in the aforementioned general formula—O—R⁵⁰—C(═O)—O—R⁵⁶ has been substituted with R⁵⁶′).

R⁴′ represents an alkylene group of 1 to 5 carbon atoms.

u is an integer of 1 to 3, and most preferably 1 or 2.

Preferable examples of the cation represented by formula (b-7) or (b-8)are shown below.

In the formula, R^(C) represents a substituent described above in theexplanation of the aforementioned substituted aryl group (an alkylgroup, an alkoxy group, an alkoxyalkyloxy group, analkoxycarbonylalkyloxy group, a halogen atom, a hydroxy group, an oxogroup (═O), an aryl group, —C(═O)—O—R⁶′, —O—C(═O)—R⁷′, and —O—R⁸′).

The anion moiety of the sulfonium salt having a cation moietyrepresented by any one of formulae (b-5) to (b-8) as a cation moietythereof is not particularly limited, and the same anion moieties foronium salt-based acid generators which have been proposed may be used.

Examples of such anion moieties include fluorinated alkylsulfonic acidions such as anion moieties (R⁴″SO₃ ⁻) for onium salt-based acidgenerators represented by general formula (b-1) or (b-2) shown above;anion moieties represented by general formula (b-3) or (b-4) shownabove; and anion moieties represented by any one of the aforementionedformula (b1) to (b9).

In the present description, an oximesulfonate acid generator is acompound having at least one group represented by general formula (B-1)shown below, and has a feature of generating acid by irradiation. Suchoximesulfonate acid generators are widely used for a chemicallyamplified resist composition, and can be appropriately selected.

In the formula, each of R³¹ and R³² independently represents an organicgroup.

The organic group for R³¹ and R³² refers to a group containing a carbonatom, and may include atoms other than carbon atoms (e.g., a hydrogenatom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom(such as a fluorine atom and a chlorine atom) and the like).

As the organic group for R³¹, a linear, branched, or cyclic alkyl groupor aryl group is preferable. The alkyl group or the aryl group may havea substituent. The substituent is not particularly limited, and examplesthereof include a fluorine atom and a linear, branched, or cyclic alkylgroup having 1 to 6 carbon atoms. The alkyl group or the aryl group “hasa substituent” means that part or all of the hydrogen atoms of the alkylgroup or the aryl group is substituted with a substituent.

The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1to 10 carbon atoms, still more preferably 1 to 8 carbon atoms, stillmore preferably 1 to 6 carbon atoms, and most preferably 1 to 4 carbonatoms. As the alkyl group, a partially or completely halogenated alkylgroup (hereinafter, sometimes referred to as a “halogenated alkylgroup”) is particularly desirable. The “partially halogenated alkylgroup” refers to an alkyl group in which part of the hydrogen atoms aresubstituted with halogen atoms and the “completely halogenated alkylgroup” refers to an alkyl group in which all of the hydrogen atoms aresubstituted with halogen atoms. Examples of halogen atoms includefluorine atoms, chlorine atoms, bromine atoms and iodine atoms, andfluorine atoms are particularly desirable. In other words, thehalogenated alkyl group is preferably a fluorinated alkyl group.

The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the arylgroup, partially or completely halogenated aryl group is particularlydesirable. The “partially halogenated aryl group” refers to an arylgroup in which some of the hydrogen atoms are substituted with halogenatoms and the “completely halogenated aryl group” refers to an arylgroup in which all of hydrogen atoms are substituted with halogen atoms.

As R³¹, an alkyl group of 1 to 4 carbon atoms which has no substituentor a fluorinated alkyl group of 1 to 4 carbon atoms is particularlydesirable.

As the organic group for R³², a linear, branched, or cyclic alkyl group,aryl group, or cyano group is preferable. Examples of the alkyl groupand the aryl group for R³² include the same alkyl groups and aryl groupsas those described above for R³¹.

As R³², a cyano group, an alkyl group of 1 to 8 carbon atoms having nosubstituent or a fluorinated alkyl group of 1 to 8 carbon atoms isparticularly desirable.

Preferred examples of the oxime sulfonate acid generator includecompounds represented by general formula (B-2) or (B-3) shown below.

In the formula, R³³ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁴ represents an aryl group;and R³⁵ represents an alkyl group having no substituent or a halogenatedalkyl group.

In the formula, R³⁶ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁷ represents a divalent ortrivalent aromatic hydrocarbon group; R³⁸ represents an alkyl grouphaving no substituent or a halogenated alkyl group; and p″ represents 2or 3.

In general formula (B-2), the alkyl group having no substituent or thehalogenated alkyl group for R³³ preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbonatoms.

As R³³, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

The fluorinated alkyl group for R³³ preferably has 50% or more of thehydrogen atoms thereof fluorinated, more preferably 70% or more, andmost preferably 90% or more.

Examples of the aryl group for R³⁴ include groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring, such as aphenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, ananthryl group, and a phenanthryl group, and heteroaryl groups in whichsome of the carbon atoms constituting the ring(s) of these groups aresubstituted with hetero atoms such as an oxygen atom, a sulfur atom, anda nitrogen atom. Of these, a fluorenyl group is preferable.

The aryl group for R³⁴ may have a substituent such as an alkyl group of1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. Thealkyl group and halogenated alkyl group as the substituent preferablyhas 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms.Further, the halogenated alkyl group is preferably a fluorinated alkylgroup.

The alkyl group having no substituent or the halogenated alkyl group forR³⁵ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbonatoms, and most preferably 1 to 6 carbon atoms.

As R³⁵, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

In terms of enhancing the strength of the acid generated, thefluorinated alkyl group for R³⁵ preferably has 50% or more of thehydrogen atoms fluorinated, more preferably 70% or more, still morepreferably 90% or more. A completely fluorinated alkyl group in which100% of the hydrogen atoms are substituted with fluorine atoms isparticularly desirable.

In general formula (B-3), as the alkyl group having no substituent andthe halogenated alkyl group for R³⁶, the same alkyl group having nosubstituent and the halogenated alkyl group described above for R³³ canbe used.

Examples of the divalent or trivalent aromatic hydrocarbon group for R³⁷include groups in which one or two hydrogen atoms have been removed fromthe aryl group for R³⁴.

As the alkyl group having no substituent or the halogenated alkyl groupfor R³⁸, the same one as the alkyl group having no substituent or thehalogenated alkyl group for R³⁵ can be used.

p″ is preferably 2.

Specific examples of suitable oxime sulfonate acid generators includeα-(p-toluenesulfonyloxyimino)-benzyl cyanide,α-(p-chlorobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitrobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-benzyl cyanide,α-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(benzenesulfonyloxyimino)-thien-2-yl acetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide,α-[(p-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-4-thienyl cyanide,α-(methylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cycloheptenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclooctenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(ethylsulfonyloxyimino)-ethyl acetonitrile,α-(propylsulfonyloxyimino)-propyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclopentyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-phenyl acetonitrile,α-(methylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-phenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(ethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(propylsulfonyloxyimino)-p-methylphenyl acetonitrile, andα-(methylsulfonyloxyimino)-p-bromophenyl acetonitrile.

Further, oxime sulfonate acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 9-208554(Chemical Formulas 18 and 19 shown in paragraphs [0012] to [0014]) andoxime sulfonate acid generators disclosed in WO 2004/074242A2 (Examples1 to 40 described at pages 65 to 86) may be preferably used.

Furthermore, as preferable examples, the following can be used.

Of the aforementioned diazomethane acid generators, specific examples ofsuitable bisalkyl or bisaryl sulfonyl diazomethanes includebis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane, andbis(2,4-dimethylphenylsulfonyl)diazomethane.

Further, diazomethane acid generators disclosed in Japanese UnexaminedPatent Application, First Publication No. Hei 11-035551, JapaneseUnexamined Patent Application, First Publication No. Hei 11-035552 andJapanese Unexamined Patent Application, First Publication No. Hei11-035573 may be preferably used.

Furthermore, as examples of poly(bis-sulfonyl)diazomethanes, thosedisclosed in Japanese Unexamined Patent Application, First PublicationNo. Hei 11-322707, including1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane,1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane,1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane,1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane,1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane,1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane,1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane, and1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane, may be given.

As the component (B), one type of acid generator may be used, or two ormore types of acid generators may be used in combination.

In the resist composition of the present invention, the amount of thecomponent (B) relative to 100 parts by weight of the component (A) ispreferably 0.5 to 50 parts by weight, and more preferably 1 to 40 partsby weight.

When the amount of the component (B) is within the above-mentionedrange, formation of a resist pattern can be satisfactorily performed.Further, by virtue of the above-mentioned range, a uniform solution canbe obtained and the storage stability becomes satisfactory.

<Other Components>

[Component (D)]

The resist composition of the present invention may contain a basiccompound (D) (hereafter referred to as the component (D)) as an optionalcomponent. The component (D) functions as an acid diffusion controlagent, i.e., a quencher which traps the acid generated from thecomponent (B) upon exposure. In the present invention, a “basiccompound” refers to a compound which is basic relative to the component(A) or the component (B).

In the present invention, the component (D) may be a basic compound (D1)(hereafter, referred to as “component (D1)”) which has a cation moietyand an anion moiety, or a basic compound (D2) (hereafter, referred to as“component (D2)”) which does not fall under the definition of component(D1).

Component (D1)

As the component (D1), at least one member selected from the groupconsisting of a compound (d1-1) represented by general formula (d1-1)shown below (hereafter, referred to as “component (d1-1)”), a compound(d1-2) represented by general formula (d1-2) shown below (hereafter,referred to as “component (d1-2)”) and a compound (d1-3) represented bygeneral formula (d1-3) shown below (hereafter, referred to as “component(d1-3)”).

In the formulae, R⁴ represents a hydrocarbon group which may have asubstituent; Z^(2c) represents a hydrocarbon group of 1 to 30 carbonatoms which may have a substituent (provided that the carbon adjacent toS has no fluorine atom as a substituent); R⁵ represents an organicgroup; Y⁵ represents a linear, branched or cyclic alkylene group or anarylene group; Rf³ represents a hydrocarbon group containing a fluorineatom; and each M⁺ independently represents a sulfonium or iodoniumcation having no aromaticity.

Component (d1-1)

Anion Moiety

In formula (d1-1), R⁴ represents a hydrocarbon group which may have asubstituent.

The hydrocarbon group for R⁴ which may have a substituent may be analiphatic hydrocarbon group or an aromatic hydrocarbon group, and thesame group as X³ in the formula X³-Q¹- described above as thesubstituent for R⁴″ in general formula “R⁴″SO₃ ⁻” in the explanation ofthe structural unit (a5) can be mentioned.

Among these, as the hydrocarbon group for R⁴ which may have asubstituent, an aromatic hydrocarbon group which may have a substituentor an aliphatic cyclic group which may have a substituent is preferable,and a phenyl group or a naphthyl group which may have a substituent, ora group in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane is more preferable.

As the hydrocarbon group for R⁴ which may have a substituent, a linearor branched alkyl group or a fluorinated alkyl group is also preferable.

The linear or branched alkyl group for R⁴ preferably has 1 to 10 carbonatoms, and specific examples thereof include a linear alkyl group suchas a methyl group, an ethyl group, a propyl group, a butyl group, apentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl ora decyl group, and a branched alkyl group such as a 1-methylethyl group,a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a3-methylpentyl group or a 4-methylpentyl group.

The fluorinated alkyl group for R⁴ may be either chain-like or cyclic,but is preferably linear or branched.

The fluorinated alkyl group preferably has 1 to 11 carbon atoms, morepreferably 1 to 8, and still more preferably 1 to 4. Specific examplesinclude a group in which part or all of the hydrogen atoms constitutinga linear alkyl group (such as a methyl group, an ethyl group, a propylgroup, a butyl group, a pentyl group, a hexyl group, a heptyl group, anoctyl group, a nonyl group or a decyl group) have been substituted withfluorine atom(s), and a group in which part or all of the hydrogen atomsconstituting a branched alkyl group (such as a 1-methylethyl group, a1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a2-methylbutyl group or a 3-methylbutyl group) have been substituted withfluorine atom(s).

The fluorinated alkyl group for R⁴ may contain an atom other thanfluorine. Examples of the atom other than fluorine include an oxygenatom, a carbon atom, a hydrogen atom, an oxygen atom, a sulfur atom anda nitrogen atom.

Among these, as the fluorinated alkyl group for R⁴, a group in whichpart or all of the hydrogen atoms constituting a linear alkyl group havebeen substituted with fluorine atom(s) is preferable, and a group inwhich all of the hydrogen atoms constituting a linear alkyl group havebeen substituted with fluorine atoms (i.e., a perfluoroalkyl group) ismore preferable.

Specific examples of preferable anion moieties for the component (d1-1)are shown below.

Cation Moiety

In formula (d1-1), M⁺ represents an organic cation.

The organic cation for M⁺ is not particularly limited, and examplesthereof include the same cation moieties as those of compoundsrepresented by the aforementioned formula (b-1) or (b-2).

As the component (d1-1), one type of compound may be used, or two ormore types of compounds may be used in combination.

Component (d1-2)

Anion Moiety

In formula (d1-2), Z^(2c) represents a hydrocarbon group of 1 to 30carbon atoms which may have a substituent.

The hydrocarbon group of 1 to 30 carbon atoms for Z² which may have asubstituent may be either an aliphatic hydrocarbon group or an aromatichydrocarbon group, and is the same as defined for R⁴ in theaforementioned formula (d1-1).

Among these, as the hydrocarbon group for Z^(2c) which may have asubstituent, an aliphatic cyclic group which may have a substituent ispreferable, and a group in which one or more hydrogen atoms have beenremoved from adamantane, norbornane, isobornane, tricyclodecane,tetracyclododecane or camphor (which may have a substituent) is morepreferable.

The hydrocarbon group for Z^(2c) may have a substituent, and the samesubstituents as those described above for X³ in the aforementionedformula X³-Q¹- can be mentioned. However, in Z^(2c), the carbon adjacentto the S atom within SO₃ ⁻ has no fluorine atom as a substituent. Byvirtue of SO₃ ⁻ having no fluorine atom adjacent thereto, the anion ofthe component (d1-2) becomes an appropriately weak acid anion, therebyimproving the quenching ability of the component (D).

Specific examples of preferable anion moieties for the component (d1-2)are shown below.

Cation Moiety

In formula (d1-2), M⁺ is the same as defined for M⁺ in theaforementioned formula (d1-1).

As the component (d1-2), one type of compound may be used, or two ormore types of compounds may be used in combination.

Component (d1-3)

Anion Moiety

In formula (d1-3), R⁵ represents an organic group.

The organic group for R⁵ is not particularly limited, and examplesthereof include an alkyl group, an alkoxy group, —O—C(═O)—C(R^(C2))═CH₂(R^(C2) represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms) and—O—C(═O)—R^(C3) (R^(C3) represents a hydrocarbon group).

The alkyl group for R⁵ is preferably a linear or branched alkyl group of1 to 5 carbon atoms, and specific examples include a methyl group, anethyl group, a propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl group,and a neopentyl group. Part of the hydrogen atoms within the alkyl groupfor R² may be substituted with a hydroxy group, a cyano group or thelike.

The alkoxy group for R⁵ is preferably an alkoxy group of 1 to 5 carbonatoms, and specific examples thereof include a methoxy group, an ethoxygroup, an n-propoxy group, an iso-propoxy group, an n-butoxy group and atert-butoxy group. Among these, a methoxy group and an ethoxy group areparticularly desirable.

When R⁵ is —O—C(═O)—C(R^(C2))═CH₂, R^(C2) represents a hydrogen atom, analkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to5 carbon atoms.

The alkyl group of 1 to 5 carbon atoms for R^(C2) is preferably a linearor branched alkyl group of 1 to 5 carbon atoms, and specific examplesthereof include a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group and a neopentyl group.

The halogenated alkyl group for R^(C2) is a group in which part or allof the hydrogen atoms of the aforementioned alkyl group of 1 to 5 carbonatoms has been substituted with halogen atoms. Examples of the halogenatom include a fluorine atom, a chlorine atom, a bromine atom and aniodine atom, and a fluorine atom is particularly desirable.

As R^(C2), a hydrogen atom, an alkyl group of 1 to 3 carbon atoms or afluorinated alkyl group of 1 to 3 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable in terms ofindustrial availability.

When R⁵ is —O—C(═O)—R^(C3), R^(C3) represents a hydrocarbon group.

The hydrocarbon group for R^(C3) may be either an aromatic hydrocarbongroup or an aliphatic hydrocarbon group. Specific examples of thehydrocarbon group for R^(C3) include the same hydrocarbon groups asthose described for R⁴ in the aforementioned formula (d1-1).

Among these, as the hydrocarbon group for R^(C3), an alicyclic group(e.g., a group in which one or more hydrogen atoms have been removedfrom a cycloalkane such as cyclopentane, cyclohexane, adamantane,norbornane, isobornane, tricyclodecane or tetracyclododecane) or anaromatic group (e.g., a phenyl group or a naphthyl group) is preferable.When R^(C3) is an alicyclic group, the resist composition can besatisfactorily dissolved in an organic solvent, thereby improving thelithography properties. Alternatively, when R^(C3) is an aromatic group,the resist composition exhibits an excellent photoabsorption efficiencyin a lithography process using EUV or the like as the exposure source,thereby resulting in the improvement of the sensitivity and thelithography properties.

Among these, as R⁵, —O—C(═O)—C(R^(C2)′)═CH₂ (R^(C2)′ represents ahydrogen atom or a methyl group) or —O—C(═O)—R^(C3)′ (R^(C3)′ representsan aliphatic cyclic group) is preferable.

In formula (d1-3), Y⁵ represents a linear, branched or cyclic alkylenegroup or an arylene group.

Examples of the linear, branched or cyclic alkylene group or the arylenegroup for Y⁵ include the “linear or branched aliphatic hydrocarbongroup”, “cyclic aliphatic hydrocarbon group” and “aromatic hydrocarbongroup” described above as the divalent linking group for R² in theaforementioned formula (a5-0).

Among these, as Y⁵, an alkylene group is preferable, a linear orbranched alkylene group is more preferable, and a methylene group or anethylene group is still more preferable.

In formula (d1-3), Rf³ represents a hydrocarbon group containing afluorine atom.

The hydrocarbon group containing a fluorine atom for Rf³ is preferably afluorinated alkyl group, and more preferably the same fluorinated alkylgroups as those described above for R⁴.

Specific examples of preferable anion moieties for the component (d1-3)are shown below.

Cation Moiety

In formula (d1-3), M⁺ is the same as defined for M⁺ in theaforementioned formula (d1-1).

As the component (d1-3), one type of compound may be used, or two ormore types of compounds may be used in combination.

The component (D1) may contain one of the aforementioned components(d1-1) to (d1-3), or at least two of the aforementioned components(d1-1) to (d1-3). In particular, it is preferable to include thecomponent (d1-1) or the component (d1-2).

The amount of the component (D1) relative to 100 parts by weight of thecomponent (A) is preferably within a range from 0.5 to 10 parts byweight, more preferably from 0.5 to 8 parts by weight, still morepreferably from 1 to 8 parts by weight, and most preferably from 1 to 5parts by weight.

When the amount of at least as large as the lower limit of theabove-mentioned range, excellent lithography properties and excellentresist pattern shape can be obtained. On the other hand, when the amountof the component (D) is no more than the upper limit of theabove-mentioned range, sensitivity can be maintained at a satisfactorylevel, and through-top becomes excellent.

(Production Method of Components (d1-1) to (d1-3))

The production methods of the components (d1-1) and (d1-2) are notparticularly limited, and the components (d1-1) and (d1-2) can beproduced by conventional methods.

The production method of the component (d1-3) is not particularlylimited. For example, in the case where R⁵ in formula (d1-3) is a grouphaving an oxygen atom on the terminal thereof which is bonded to Y⁵, thecompound (d1-3) represented by general formula (d1-3) can be produced byreacting a compound (i-1) represented by general formula (i-1) shownbelow with a compound (i-2) represented by general formula (i-2) shownbelow to obtain a compound (i-3) represented by general formula (i-3),and reacting the compound (i-3) with a compound Z⁻M⁺ having the desiredcation M⁺, thereby obtaining the compound (d1-3).

In the formulae, R⁵, Y⁵, Rf³ and M⁺ are respectively the same as definedfor R⁵, Y⁵, Rf³ and M⁺ in the aforementioned general formula (d1-3);R^(5a) represents a group in which the terminal oxygen atom has beenremoved from R⁵; and Z⁻ represents a counteranion.

Firstly, the compound (i-1) is reacted with the compound (i-2), tothereby obtain the compound (i-3).

In formula (i-1), R^(5a) represents a group in which the terminal oxygenatom has been removed from R⁵. In formula (i-2), Y⁵ and Rf³ are the sameas defined above.

As the compound (i-1) and the compound (i-2), commercially availablecompounds may be used, or the compounds may be synthesized.

The method for reacting the compound (i-1) with the compound (i-2) toobtain the compound (i-3) is not particularly limited, but can beperformed, for example, by reacting the compound (i-1) with the compound(i-2) in an organic solvent in the presence of an appropriate acidiccatalyst, followed by washing and recovering the reaction mixture.

The acidic catalyst used in the above reaction is not particularlylimited, and examples thereof include toluenesulfonic acid and the like.The amount of the acidic catalyst is preferably 0.05 to 5 moles, per 1mole of the compound (i-2).

As the organic solvent used in the above reaction, any organic solventwhich is capable of dissolving the raw materials, i.e., the compound(i-1) and the compound (i-2) can be used, and specific examples thereofinclude toluene and the like. The amount of the organic solvent ispreferably 0.5 to 100 parts by weight, more preferably 0.5 to 20 partsby weight, relative to the amount of the compound (i-1). As the solvent,one type may be used alone, or two or more types may be used incombination.

In general, the amount of the compound (i-2) used in the above reactionis preferably 0.5 to 5 moles per 1 mole of the compound (i-1), and morepreferably 0.8 to 4 moles per 1 mole of the compound (i-1).

The reaction time depends on the reactivity of the compounds (i-1) and(i-2), the reaction temperature or the like. However, in general, thereaction time is preferably 1 to 80 hours, and more preferably 3 to 60hours.

The reaction temperature in the above reaction is preferably 20 to 200°C., and more preferably 20 to 150° C.

Next, the obtained compound (i-3) is reacted with the compound (i-4),thereby obtaining the compound (d1-3).

In formula (i-4), M⁺ is the same as defined above, and Z⁻ represents acounteranion.

The method for reacting the compound (i-3) with the compound (i-4) toobtain the compound (d1-3) is not particularly limited, but can beperformed, for example, by dissolving the compound (i-3) in an organicsolvent and water in the presence of an appropriate alkali metalhydroxide, followed by addition of the compound (i-4) and stirring.

The alkali metal hydroxide used in the above reaction is notparticularly limited, and examples thereof include sodium hydroxide,potassium hydroxide and the like. The amount of the alkali metalhydroxide is preferably 0.3 to 3 moles, per 1 mole of the compound(i-3).

Examples of the organic solvent used in the above reaction includedichloromethane, chloroform, ethyl acetate and the like. The amount ofthe organic solvent is preferably 0.5 to 100 parts by weight, and morepreferably 0.5 to 20 parts by weight, relative to the weight of thecompound (i-3). As the solvent, one type may be used alone, or two ormore types may be used in combination.

In general, the amount of the compound (i-4) used in the above reactionis preferably 0.5 to 5 moles per 1 mole of the compound (i-3), and morepreferably 0.8 to 4 moles per 1 mole of the compound (i-3).

The reaction time depends on the reactivity of the compounds (i-3) and(i-4), the reaction temperature or the like. However, in general, thereaction time is preferably 1 to 80 hours, and more preferably 3 to 60hours.

The reaction temperature in the above reaction is preferably 20 to 200°C., and more preferably 20 to 150° C.

After the reaction, the compound (d1-3) contained in the reactionmixture may be separated and purified. The separation and purificationcan be conducted by a conventional method. For example, any one ofconcentration, solvent extraction, distillation, crystallization,recrystallization and chromatography can be used alone, or two or moreof these methods may be used in combination.

The structure of the compound (d1-3) obtained in the manner describedabove can be confirmed by a general organic analysis method such as¹H-nuclear magnetic resonance (NMR) spectrometry, ¹³C-NMR spectrometry,¹⁹F-NMR spectrometry, infrared absorption (IR) spectrometry, massspectrometry (MS), elementary analysis and X-ray diffraction analysis.

Component (D2)

The component (D2) is not particularly limited, as long as it is acompound which is basic relative to the component (B), so as tofunctions as an acid diffusion control agent, i.e., a quencher whichtraps the acid generated from the component (B) upon exposure, and doesnot fall under the definition of the component (D1). As the component(D2), any of the conventionally known compounds may be selected for use.Examples thereof include an aliphatic amine and an aromatic amine. Amongthese, an aliphatic amine is preferable, and a secondary aliphatic amineor tertiary aliphatic amine is particularly desirable.

An aliphatic amine is an amine having one or more aliphatic groups, andthe aliphatic groups preferably have 1 to 12 carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of no more than 20 carbon atoms (i.e., alkylaminesor alkylalcoholamines), cyclic amines, and other aliphatic amines.

The alkyl group within the alkylamine may be linear, branched or cyclic.

When the alkyl group is linear or branched, the alkyl group preferablyhas 2 to 20 carbon atoms, and more preferably 2 to 8 carbon atoms.

When the alkyl group is cyclic (i.e., a cycloalkyl group), the number ofcarbon atoms is preferably 3 to 30, more preferably 3 to 20, still morepreferably 3 to 15, still more preferably 4 to 12, and most preferably 5to 10. The alkyl group may be monocyclic or polycyclic. Examples thereofinclude groups in which one or more of the hydrogen atoms have beenremoved from a monocycloalkane; and groups in which one or more of thehydrogen atoms have been removed from a polycycloalkane such as abicycloalkane, a tricycloalkane, or a tetracycloalkane. Specificexamples of the monocycloalkane include cyclopentane and cyclohexane.Specific examples of the polycycloalkane include adamantane, norbornane,isobornane, tricyclodecane and tetracyclododecane.

As the alkyl group within the hydroxyalkyl group of thealkylalcoholamine, the same alkyl groups as those described above forthe alkylamines can be mentioned.

Specific examples of alkylamines include monoalkylamines such asn-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, andn-decylamine; dialkylamines such as diethylamine, di-n-propylamine,di-n-heptylamine, di-n-octylamine, and dicyclohexylamine; trialkylaminessuch as trimethylamine, triethylamine, tri-n-propylamine,tri-n-butylamine, tri-n-hexylamine, tri-n-pentylamine,tri-n-heptylamine, tri-n-octylamine, tri-n-nonylamine,tri-n-decanylamine, and tri-n-dodecylamine.

Specific examples of alkylalcoholamines include diethanolamine,triethanolamine, diisopropanolamine, triisopropanolamine,di-n-octanolamine, tri-n-octanolamine, stearyldiethanolamine andlauryldiethanolamine.

Among these, trialkylamines of 5 to 10 carbon atoms are preferable, andtri-n-pentylamine and tri-n-octylamine are particularly desirable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine,and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine and triethanolamine triacetate.

Examples of aromatic amines include aniline, pyridine,4-dimethylaminopyridine, pyrrole, indole, pyrazole, imidazole andderivatives thereof, as well as diphenylamine, triphenylamine,tribenzylamine, 2,6-diisopropylaniline andN-tert-butoxycarbonylpyrrolidine.

As the component (D2), one type of compound may be used, or two or moretypes of compounds may be used in combination.

The component (D2) is typically used in an amount within a range from0.01 to 5 parts by weight, relative to 100 parts by weight of thecomponent (A). When the amount of the component (D) is within theabove-mentioned range, the shape of the resist pattern and the postexposure stability of the latent image formed by the pattern-wiseexposure of the resist layer are improved.

As the component (D), one type of compound may be used, or two or moretypes of compounds may be used in combination.

When the resist composition of the present invention contains thecomponent (D), the amount of the component (D) (the total amount of thecomponent (D1) and the component (D2)) relative to 100 parts by weightof the component (A) is preferably within a range from 0.1 to 15 partsby weight, more preferably from 0.3 to 12 parts by weight, and stillmore preferably from 0.5 to 12 parts by weight.

When the amount of the component (D) is at least as large as the lowerlimit of the above-mentioned range, various lithography properties suchas roughness are improved. Further, a resist pattern having an excellentshape can be obtained. On the other hand, when the amount of thecomponent (D) is no more than the upper limit of the above-mentionedrange, sensitivity can be maintained at a satisfactory level, andthrough-top becomes excellent.

[Component (E)]

Furthermore, in the resist composition of the present invention, forpreventing any deterioration in sensitivity, and improving the resistpattern shape and the post exposure stability of the latent image formedby the pattern-wise exposure of the resist layer, at least one compound(E) (hereafter referred to as “component (E)”) selected from the groupconsisting of an organic carboxylic acid, or a phosphorus oxo acid orderivative thereof can be added.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids include phosphoric acid, phosphonicacid and phosphinic acid. Among these, phosphonic acid is particularlydesirable.

Examples of oxo acid derivatives include esters in which a hydrogen atomwithin the above-mentioned oxo acids is substituted with a hydrocarbongroup. Examples of the hydrocarbon group include an alkyl group of 1 to5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid esterssuch as phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more typesmay be used in combination.

In the present invention, when the resist composition contains thecomponent (E), the amount of the component (E) is used in an amountwithin a range from 0.01 to 5 parts by weight, relative to 100 parts byweight of the component (A).

If desired, other miscible additives can also be added to the resistcomposition of the present invention. Examples of such miscibleadditives include additive resins for improving the performance of theresist film, surfactants for improving the applicability, dissolutioninhibitors, plasticizers, stabilizers, colorants, halation preventionagents, and dyes.

[Component (S)]

The resist composition for immersion exposure according to the presentinvention can be prepared by dissolving the resist materials for theresist composition in an organic solvent (hereafter, frequently referredto as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and one or more kindsof any organic solvent can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methyl ethyl ketone, cyclohexanone (CH), methyl-n-pentylketone, methyl isopentyl ketone, and 2-heptanone; polyhydric alcohols,such as ethylene glycol, diethylene glycol, propylene glycol anddipropylene glycol; compounds having an ester bond, such as ethyleneglycol monoacetate, diethylene glycol monoacetate, propylene glycolmonoacetate, and dipropylene glycol monoacetate; polyhydric alcoholderivatives including compounds having an ether bond, such as amonoalkylether (e.g., monomethylether, monoethylether, monopropyletheror monobutylether) or monophenylether of any of these polyhydricalcohols or compounds having an ester bond (among these, propyleneglycol monomethyl ether acetate (PGMEA) and propylene glycol monomethylether (PGME) are preferable); cyclic ethers such as dioxane; esters suchas methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate,butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; and aromatic organicsolvents such as anisole, ethylbenzylether, cresylmethylether,diphenylether, dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene.

These solvents can be used individually, or in combination as a mixedsolvent.

Among these, γ-butyrolactone, propylene glycol monomethyl ether acetate(PGMEA), propylene glycol monomethyl ether (PGME), cyclohexanone (CH)and ethyl lactate (EL) are preferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2. For example, when EL is mixed as the polar solvent, the PGMEA:ELweight ratio is preferably from 1:9 to 9:1, and more preferably from 2:8to 8:2. Alternatively, when PGME is mixed as the polar solvent, thePGMEA:PGME weight ratio is preferably from 1:9 to 9:1, more preferablyfrom 2:8 to 8:2, and still more preferably 3:7 to 7:3. Alternatively,when PGME and cyclohexanone is mixed as the polar solvent, thePGMEA:(PGME+cyclohexanone) weight ratio is preferably from 1:9 to 9:1,more preferably from 2:8 to 8:2, and still more preferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of γ-butyrolactone withPGMEA, EL or the aforementioned mixed solvent of PGMEA with a polarsolvent, is also preferable. The mixing ratio (former:latter) of such amixed solvent is preferably from 70:30 to 95:5.

The amount of the organic solvent is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate, depending on the thickness of thecoating film. In general, the organic solvent is used in an amount suchthat the solid content of the resist composition becomes within therange from 1 to 20% by weight, and preferably from 2 to 15% by weight.

The resist composition of the present invention exhibits excellentproperties with respect to sensitivity, resolution, lithographyproperties and etching resistance. The reason why these effects can beachieved has not been elucidated yet, but is presumed as follows.

In the resist composition of the present invention, the polymericcompound (A1) includes a structural unit (a5) represented by generalformula (a5-0). The structural unit (a5) has an imino group (—NH—), andadjacent to the imino group, a carbonyl group (—C(═O)—) on one side anda carbonyl group or a thioketone (—C(═S)—) on the other side. By virtueof such a structure, the acidic proton on the nitrogen atom of the iminogroup functions as a proton source, and in particular, a highsensitivity can be achieved. In addition, by the presence of thenitrogen atom of the imino group, diffusion of acid generated from thecomponent (B) upon exposure can be suppressed, and in particular,resolution and lithography properties can be improved. Furthermore,since the imino group is present in the polymeric compound, the nitrogenatom can be uniformly distributed within the resist film, and the effectof suppressing diffusion of acid can be homogeneously obtained in theentire resist film. Moreover, the presence of an aromatic ring or apolycyclic group within Y in the structural unit (a5), in particular,contributes to improving etching resistance of the resist pattern.Furthermore, by introducing an aromatic ring or a polycyclic group, theheat resistance of the resist film can be improved, thereby improvinglithography properties such as pattern roughness. For the reasons asdescribed above, it is presumed that the effects of the presentinvention can be achieved.

<<Method of Forming a Resist Pattern>>

The method of forming a resist pattern according to the presentinvention includes: forming a resist film on a substrate using a resistcomposition of the present invention; conducting exposure of the resistfilm; and developing the resist film to form a resist pattern.

The method for forming a resist pattern according to the presentinvention can be performed, for example, as follows.

Firstly, a resist composition of the present invention is applied to asubstrate using a spinner or the like, and a bake treatment (postapplied bake (PAB)) is conducted at a temperature of 80 to 150° C. for40 to 120 seconds, preferably 60 to 90 seconds, to form a resist film.

Following selective exposure of the thus formed resist film, either byexposure through a mask having a predetermined pattern formed thereon(mask pattern) using an exposure apparatus such as an ArF exposureapparatus, an electron beam lithography apparatus or an EUV exposureapparatus, or by patterning via direct irradiation with an electron beamwithout using a mask pattern, baking treatment (post exposure baking(PEB)) is conducted under temperature conditions of 80 to 150° C. for 40to 120 seconds, and preferably 60 to 90 seconds.

Next, the resist film is subjected to a developing treatment.

The developing treatment is conducted using an alkali developingsolution in the case of an alkali developing process, and a developingsolution containing an organic solvent (organic developing solution) inthe case of a solvent developing process.

After the developing treatment, it is preferable to conduct a rinsetreatment. The rinse treatment is preferably conducted using pure waterin the case of an alkali developing process, and a rinse solutioncontaining an organic solvent in the case of a solvent developingprocess.

In the case of a solvent developing process, after the developingtreatment or the rinsing, the developing solution or the rinse liquidremaining on the pattern can be removed by a treatment using asupercritical fluid.

After the developing treatment or the rinse treatment, drying isconducted. If desired, bake treatment (post bake) can be conductedfollowing the developing. In this manner, a resist pattern can beobtained.

The substrate is not specifically limited and a conventionally knownsubstrate can be used. For example, substrates for electroniccomponents, and such substrates having wiring patterns formed thereoncan be used. Specific examples of the material of the substrate includemetals such as silicon wafer, copper, chromium, iron and aluminum; andglass. Suitable materials for the wiring pattern include copper,aluminum, nickel, and gold.

Further, as the substrate, any one of the above-mentioned substratesprovided with an inorganic and/or organic film on the surface thereofmay be used. As the inorganic film, an inorganic antireflection film(inorganic BARC) can be used. As the organic film, an organicantireflection film (organic BARC) and an organic film such as alower-layer organic film used in a multilayer resist method can be used.

Here, a “multilayer resist method” is method in which at least one layerof an organic film (lower-layer organic film) and at least one layer ofa resist film (upper resist film) are provided on a substrate, and aresist pattern formed on the upper resist film is used as a mask toconduct patterning of the lower-layer organic film. This method isconsidered as being capable of forming a pattern with a high aspectratio. More specifically, in the multilayer resist method, a desiredthickness can be ensured by the lower-layer organic film, and as aresult, the thickness of the resist film can be reduced, and anextremely fine pattern with a high aspect ratio can be formed.

The multilayer resist method is broadly classified into a method inwhich a double-layer structure consisting of an upper-layer resist filmand a lower-layer organic film is formed (double-layer resist method),and a method in which a multilayer structure having at least threelayers consisting of an upper-layer resist film, a lower-layer organicfilm and at least one intermediate layer (thin metal film or the like)provided between the upper-layer resist film and the lower-layer organicfilm (triple-layer resist method).

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiation such as ArF excimer laser,KrF excimer laser, F₂ excimer laser, extreme ultraviolet rays (EUV),vacuum ultraviolet rays (VUV), electron beam (EB), X-rays, and softX-rays. The resist composition of the present invention is effective toKrF excimer laser, ArF excimer laser, EB and EUV.

The exposure of the resist film can be either a general exposure (dryexposure) conducted in air or an inert gas such as nitrogen, orimmersion exposure (immersion lithography).

In immersion lithography, the region between the resist film and thelens at the lowermost point of the exposure apparatus is pre-filled witha solvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film to be exposed. The refractive index of the immersion mediumis not particularly limited as long at it satisfies the above-mentionedrequirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film include water, fluorine-based inertliquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the removal of theimmersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

As the immersion medium, water is preferable in terms of cost, safety,environment and versatility.

As an example of the alkali developing solution used in an alkalideveloping process, a 0.1 to 10% by weight aqueous solution oftetramethylammonium hydroxide (TMAH) can be given.

As the organic solvent contained in the organic developing solution usedin a solvent developing process, any of the conventional organicsolvents can be used which are capable of dissolving the component (A)(prior to exposure). Specific examples of the organic solvent includepolar solvents such as ketone solvents, ester solvents, alcoholsolvents, amide solvents and ether solvents, and hydrocarbon solvents.

If desired, the organic developing solution may have a conventionaladditive blended. Examples of the additive include surfactants. Thesurfactant is not particularly limited, and for example, an ionic ornon-ionic fluorine and/or silicone surfactant can be used.

When a surfactant is added, the amount thereof based on the total amountof the organic developing solution is generally 0.001 to 5% by weight,preferably 0.005 to 2% by weight, and more preferably 0.01 to 0.5% byweight.

The developing treatment can be performed by a conventional developingmethod. Examples thereof include a method in which the substrate isimmersed in the developing solution for a predetermined time (a dipmethod), a method in which the developing solution is cast up on thesurface of the substrate by surface tension and maintained for apredetermined period (a puddle method), a method in which the developingsolution is sprayed onto the surface of the substrate (spray method),and a method in which the developing solution is continuously ejectedfrom a developing solution ejecting nozzle while scanning at a constantrate to apply the developing solution to the substrate while rotatingthe substrate at a constant rate (dynamic dispense method).

As the organic solvent contained in the rinse liquid used in the rinsetreatment after the developing treatment in the case of a solventdeveloping process, any of the aforementioned organic solvents containedin the organic developing solution can be used which hardly dissolvesthe resist pattern. In general, at least one solvent selected from thegroup consisting of hydrocarbon solvents, ketone solvents, estersolvents, alcohol solvents, amide solvents and ether solvents is used.Among these, at least one solvent selected from the group consisting ofhydrocarbon solvents, ketone solvents, ester solvents, alcohol solventsand amide solvents is preferable, more preferably at least one solventselected from the group consisting of alcohol solvents and estersolvents, and an alcohol solvent is particularly desirable.

The rinse treatment using a rinse liquid (washing treatment) can beconducted by a conventional rinse method. Examples of the rinse methodinclude a method in which the rinse liquid is continuously applied tothe substrate while rotating it at a constant rate (rotational coatingmethod), a method in which the substrate is immersed in the rinse liquidfor a predetermined time (dip method), and a method in which the rinseliquid is sprayed onto the surface of the substrate (spray method).

<<Compound>>

The compound of the present invention is represented by general formula(1) shown below (hereafter, referred to as “compound (1)”).

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R¹represents a sulfur atom or an oxygen atom; R² represents a single bondor a divalent linking group; and Y represents an aromatic hydrocarbongroup or an aliphatic hydrocarbon group having a polycyclic group,provided that the aromatic hydrocarbon group or the aliphatichydrocarbon may have a carbon atom or a hydrogen atom thereofsubstituted with a substituent.

In the formula (1), R, R¹, R² and Y are respectively the same as definedfor R, R¹, R² and Y in the aforementioned formula (a5-0).

The compound (1) is useful as a monomer for producing the component(A1).

(Production Method of Compound (1))

The production method of the compound (1) of the present invention isnot particularly limited. For example, the compound (1) can be producedby reacting a compound (1-1) represented by formula (1-1) shown belowwith a compound (1-2) represented by formula (1-2) shown below.

In the formulae, R, R¹, R² and Y are respectively the same as definedfor R, R¹, R² and Y in the aforementioned formula (a5-0); and Xhrepresents a halogen atom.In the formula (1-2), Xh represents a halogen atom, and examples thereofinclude a fluorine atom, a chlorine atom, a bromine atom and an iodineatom, and a chlorine atom is preferable.

The compound (1-1) can be reacted with the compound (1-2), for example,as follows. The compound (1-1) is dissolved in an appropriate organicsolvent, followed by stirring in the presence of an appropriate base.Then, the compound (1-2) is added thereto and stirred, followed bywashing and recovering the reaction mixture.

As a compound (1-1) and a compound (1-2), commercially availablecompounds can be used. Alternatively, a compound (1-1) and a compound(1-2) can be synthesized.

In the above reaction, as the organic solvent, tetrahydrofuran,tert-butylmethylether, dichloromethane (methylene chloride),acetonitrile, chloroform or the like is preferable, and the amount ofthe organic solvent, relative to 100 parts by weight of the compound(1-1) is preferably 0.5 to 100 parts by weight, and more preferably 0.5to 20 parts by weight. As the organic solvent, one type may be usedalone, or two or more types may be used in combination.

Examples of the base include sodium hydride, K₂CO₃, Cs₂CO₃, lithiumdiisopropylamide (LiDA), triethylamine and 4-dimethylaminopyridine.These bases may be used individually or in a combination of two or more.The base may be used in a catalyst amount. In general, the amount of thebase is 0.01 to 10 moles, per 1 mole of the compound (1-1).

The reaction time depends on the reactivity of the compounds (1-1) and(1-2), the reaction temperature or the like. However, in general, thereaction time is preferably 0.1 to 100 hours, and more preferably 0.5 to50 hours.

The reaction temperature in the above reaction is preferably 0 to 50°C., and more preferably 0 to 30° C.

In general, the amount of the compound (1-2) used in the above reactionis preferably 0.5 to 10 moles per 1 mole of the compound (1-1), and morepreferably 0.5 to 5 moles per 1 mole of the compound (1-1).

After the reaction, the compound (1) within the reaction mixture may beseparated and purified.

The separation and purification can be conducted by a conventionalmethod. For example, any one of concentration, solvent extraction,distillation, crystallization, recrystallization and chromatography canbe used alone, or two or more of these methods may be used incombination.

The structure of the compound (1) obtained in the manner described abovecan be confirmed by a general organic analysis method such as ¹H-nuclearmagnetic resonance (NMR) spectrometry, ¹³C-NMR spectrometry, ¹⁹F-NMRspectrometry, infrared absorption (IR) spectrometry, mass spectrometry(MS), elementary analysis and X-ray diffraction analysis.

<<Polymeric Compound>>

The polymeric compound of the present invention includes a structuralunit (a5) represented by general formula (a5-0) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R¹represents a sulfur atom or an oxygen atom; R² represents a single bondor a divalent linking group; and Y represents an aliphatic hydrocarbongroup having an aromatic hydrocarbon group or a polycyclic group,provided that the aromatic hydrocarbon group or the polycyclic group mayhave a carbon atom or a hydrogen atom thereof substituted with asubstituent.

In the polymeric compound of the present invention, the amount of thestructural unit (a5), based on the combined total of all the structuralunits that constitute the polymeric compound is preferably 5 to 70 mol%.

It is preferable that the polymeric compound of the present inventionfurther includes a structural unit (a1)) containing an acid decomposablegroup that exhibits increased polarity by the action of acid.

The explanation of the polymeric compound of the present invention isthe same as the explanation of the component (A1) of the resistcomposition of the present invention described above.

The polymeric compound of the present invention is preferable as a baseresin of a resist composition.

EXAMPLES

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

In the following examples, a compound represented by a chemical formula(1) is designated as “compound (1)”, and the same applies for compoundsrepresented by other chemical formulae.

Monomer Synthesis Example: Examples 1 to 9 Example 1

90.0 g of methacrylamide was dissolved in 1,350 g of tetrahydrofuran(THF), and 944 mL of a 1.12 mol/L lithium diisopropylamide (LiDA)solution was dropwise added thereto at 5° C., followed by stirring for10 minutes. Subsequently, 900 g of THF having 231.1 g of1-adamantanecarbonyl chloride dissolved therein was added thereto,followed by stirring at 5° C. for 18 hours. After completion of thereaction, THF and t-butylmethylether (TBME) were added thereto, followedby washing with a 1 wt % aqueous hydrochloric acid solution and purewater, and concentration under reduced pressure. n-hexane was added tothe obtained solution, and crystallization was conducted at 5° C.,followed by filtration. The obtained solid was dried under reducedpressure, thereby obtaining 194.4 g of 1-adamantanecarboxylic acidmethacrylamide (compound (51)).

With respect to the obtained compound (51), the results of the protonnuclear magnetic resonance spectrum (¹H-NMR) are shown below.

¹H-NMR (DMSO-d6, internal standard: tetramethylsilane): δ=9.85 ppm (brs, 1H), 5.57 ppm (s, 1H), 5.51 ppm (s, 1H), 1.98 ppm (m, 3H), 1.86 ppm(m, 9H), 1.61 ppm (m, 6H)

Example 2

The same procedure as in Example 1 was performed, thereby obtaining acompound (52).

With respect to the obtained compound (52), the results of the protonnuclear magnetic resonance spectrum (¹H-NMR) are shown below.

¹H-NMR (DMSO-d6, internal standard: tetramethylsilane): δ=9.08 ppm (brs, 1H), 6.21 ppm (s, 1H), 5.62 ppm (s, 1H), 4.95 ppm (s, 2H), 2.10 ppm(m, 3H), 1.95 ppm (s, 3H), 1.71 ppm (m, 6H), 1.56 ppm (m, 6H)

Example 3

The same procedure as in Example 1 was performed, thereby obtaining acompound (53).

With respect to the obtained compound (53), the results of the protonnuclear magnetic resonance spectrum (¹H-NMR) are shown below.

¹H-NMR (DMSO-d6, internal standard: tetramethylsilane): δ=9.76 ppm (brs, 1H), 5.58 ppm (s, 1H), 5.46 ppm (s, 1H), 2.53 ppm (s, 2H), 1.92 ppm(m, 6H), 1.57 ppm (m, 6H), 1.50 ppm (m, 6H)

Example 4

The same procedure as in Example 1 was performed, thereby obtaining acompound (54).

With respect to the obtained compound (54), the results of the protonnuclear magnetic resonance spectrum (¹H-NMR) are shown below.

¹H-NMR (DMSO-d6, internal standard: tetramethylsilane): δ=10.08 ppm (brs, 1H), 5.85 ppm (s, 1H), 5.37 ppm (s, 1H), 2.48-1.70 ppm (m, 7H), 1.13ppm (s, 3H), 1.06 ppm (s, 3H), 0.97 ppm (s, 3H)

Example 5

The same procedure as in Example 1 was performed, thereby obtaining acompound (55).

With respect to the obtained compound (55), the results of the protonnuclear magnetic resonance spectrum (¹H-NMR) are shown below.

¹H-NMR (DMSO-d6, internal standard: tetramethylsilane): δ=10.10 ppm (brs, 1H), 8.50-7.47 ppm (m, 7H), 5.58 ppm (s, 1H), 5.51 ppm (s, 1H), 1.93ppm (s, 3H)

Example 6

The same procedure as in Example 1 was performed, thereby obtaining acompound (56).

With respect to the obtained compound (56), the results of the protonnuclear magnetic resonance spectrum (¹H-NMR) are shown below.

¹H-NMR (DMSO-d6, internal standard: tetramethylsilane): δ=10.01 ppm (brs, 1H), 7.98-7.45 ppm (s, 5H), 5.60 ppm (s, 1H), 5.55 ppm (s, 1H), 1.85ppm (s, 3H)

Example 7

The same procedure as in Example 1 was performed, thereby obtaining acompound (57).

With respect to the obtained compound (57), the results of the protonnuclear magnetic resonance spectrum (¹H-NMR) are shown below.

¹H-NMR (DMSO-d6, internal standard: tetramethylsilane): δ=10.12 ppm (brs, 1H), 5.63 ppm (s, 1H), 5.56 ppm (s, 1H), 2.26 ppm (s, 6H), 2.19 ppm(s, 3H), 2.04 ppm (s, 6H), 1.87 ppm (s, 3H)

Example 8

The same procedure as in Example 1 was performed, thereby obtaining acompound (58).

With respect to the obtained compound (58), the results of the protonnuclear magnetic resonance spectrum (¹H-NMR) are shown below.

¹H-NMR (DMSO-d6, internal standard: tetramethylsilane): δ=11.01 ppm (brs, 1H), 5.82 ppm (s, 1H), 5.66 ppm (s, 1H)

Example 9

The same procedure as in Example 1 was performed, thereby obtaining acompound (59).

With respect to the obtained compound (59), the results of the protonnuclear magnetic resonance spectrum (¹H-NMR) are shown below.

¹H-NMR (DMSO-d6, internal standard: tetramethylsilane): δ=11.84 ppm (brs, 1H), 6.04 ppm (s, 1H), 5.85 ppm (s, 1H)

The structure of the obtained compounds (52) to (59) are shown below.

Polymer Synthesis Examples Examples 10 to 26, Comparative Examples 1 and2 Example 10

In a separable flask equipped with a thermometer, a reflux tube and anitrogen feeding pipe, 25.4 g (96.82 mmol) of a compound (11) wasdissolved in a mixed solvent containing 18.79 g of methyl ethyl ketone(MEK) and 18.79 g of cyclohexanone (CH), and heated to 80° C. To theresulting solution was added a solution obtained by dissolving 10.00 g(58.77 mmol) of a compound (21), 6.35 g (24.20 mmol) of a compound (11),10.48 mmol (42.38 mmol) of the compound (51) and 24.44 mmol of dimethyl2,2′-azobis(isobutyrate) (V-601) as a polymerization initiator in 44.88g of MEK and 44.88 g of CH in a dropwise manner over 4 hours in anitrogen atmosphere.

Thereafter, the reaction solution was heated for 1 hour while stirring,and then cooled to room temperature. The obtained reaction polymersolution was dropwise added to an excess amount of n-heptane, and anoperation to deposit a polymer was conducted. Thereafter, theprecipitated white powder was separated by filtration, followed bywashing with methanol and drying, thereby obtaining 31.2 g of apolymeric compound (1) as an objective compound.

With respect to the polymeric compound (1), the weight average molecularweight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 6,800, and the dispersity was 1.72. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was l/m/n=41.7/39.9/18.4.

Examples 11 to 26, Comparative Examples 1 and 2

Polymeric compounds (2) to (19) were synthesized in the same manner asin Example 10, except that the aforementioned compounds (51) to (59) andthe following compounds (10) to (15), (21), (22), (31) and (32) whichderived the structural units constituting each polymeric compound wereused in predetermined molar ratio.

With respect to each polymeric compound, the structural units forderiving the compound, the copolymer compositional ratio as determinedby carbon 13 nuclear magnetic resonance spectrometry (600 MHz_(—)¹³C-NMR) and the weight average molecular weight and the dispersity(Mw/Mn) determined by the polystyrene equivalent value as measured bygel permeation chromatography (GPC) are shown in Table 1.

TABLE 1 Polymeric Structural units for Copolymer compositional compoundderiving compound ratio Mw Mw/Mn Ex. 10 (1) (21)/(11)/(51)41.7/39.9/18.4 6800 1.72 Ex. 11 (2) (21)/(12)/(51) 43.7/39.9/16.4 73001.68 Ex. 12 (3) (21)/(13)/(51) 41.6/38.8/19.6 5800 1.72 Ex. 13 (4)(22)/(11)/(51) 42.9/39.2/17.9 6100 1.80 Ex. 14 (5) (22)/(14)/(51)43.0/37.5/19.5 7000 1.64 Ex. 15 (6) (21)/(22)/(11)/(15)/(51)34.8/21.2/17.1/13.6/13.3 6900 1.65 Ex. 16 (7) (22)/(11)/(31)/(51)28.1/40.7/9.4/21.8 6900 1.74 Ex. 17 (8) (22)/(11)/(32)/(51)27.1/42.3/9.0/21.6 6600 1.75 Ex. 18 (9) (21)/(11)/(52) 41.0/39.0/20.05500 1.66 Ex. 19 (10) (21)/(11)/(53) 44.2/38.3/17.6 6800 1.64 Ex. 20(11) (21)/(11)/(54) 42.8/37.9/19.3 7700 1.65 Ex. 21 (12) (21)/(11)/(55)41.1/37.6/21.3 7900 1.72 Comp. (13) (21)/(12)/(31) 43.4/38.5/18.1 79001.67 Ex. 1 Comp. (14) (21)/(12)/(10) 40.2/40.8/19.0 5400 1.72 Ex. 2 Ex.22 (15) (11)/(54) 39.4/60.6 8100 1.70 Ex. 23 (16) (21)/(11)/(56)43.0/38.4/18.6 6900 1.65 Ex. 24 (17) (21)/(11)/(57) 43.6/37.5/18.9 70001.64 Ex. 25 (18) (21)/(11)/(58) 44.7/36.8/18.5 5600 1.74 Ex. 26 (19)(21)/(11)/(59) 42.0/39.3/18.7 6200 1.72

<Production of Resist Composition>

Examples 27 to 47, Comparative Examples 3 to 5

The components shown in Table 2 to 4 were mixed together and dissolvedto obtain resist compositions.

TABLE 2 Compo- Compo- nent nent Component Component (A) (B) (D) (E)Component (S) Ex. 27 (A)-1 (B)-1 (D)-1 (E)-1 (S)-1 (S)-2 [100] [38.2][1.5] [0.6] [200] [5000] Ex. 28 (A)-2 (B)-1 (D)-1 (E)-1 (S)-1 (S)-2[100] [38.2] [1.5] [0.6] [200] [5000] Ex. 29 (A)-3 (B)-1 (D)-1 (E)-1(S)-1 (S)-2 [100] [38.2] [1.5] [0.6] [200] [5000] Ex. 30 (A)-4 (B)-1(D)-1 (E)-1 (S)-1 (S)-2 [100] [38.2] [1.5] [0.6] [200] [5000] Ex. 31(A)-5 (B)-1 (D)-1 (E)-1 (S)-1 (S)-2 [100] [38.2] [1.5] [0.6] [200][5000] Ex. 32 (A)-6 (B)-1 (D)-1 (E)-1 (S)-1 (S)-2 [100] [38.2] [1.5][0.6] [200] [5000] Ex. 33 (A)-7 (B)-1 (D)-1 (E)-1 (S)-1 (S)-2 [100][38.2] [1.5] [0.6] [200] [5000] Ex. 34 (A)-8 (B)-1 (D)-1 (E)-1 (S)-1(S)-2 [100] [38.2] [1.5] [0.6] [200] [5000] Ex. 35 (A)-9 (B)-1 (D)-1(E)-1 (S)-1 (S)-2 [100] [38.2] [1.5] [0.6] [200] [5000] Ex. 36 (A)-10(B)-1 (D)-1 (E)-1 (S)-1 (S)-2 [100] [38.2] [1.5] [0.6] [200] [5000] Ex.37 (A)-11 (B)-1 (D)-1 (E)-1 (S)-1 (S)-2 [100] [38.2] [1.5] [0.6] [200][5000] Ex. 38 (A)-12 (B)-1 (D)-1 (E)-1 (S)-1 (S)-2 [100] [38.2] [1.5][0.6] [200] [5000] Ex. 39 (A)-1 (B)-1 (D)-2 — (S)-1 (S)-2 [100] [38.2][2.1] [200] [5000] Comp. (A)-13 (B)-1 (D)-1 (E)-1 (S)-1 (S)-2 Ex. 3[100] [38.2] [1.5] [0.6] [200] [5000] Comp. (A)-14 (B)-1 (D)-1 (E)-1(S)-1 (S)-2 Ex. 4 [100] [38.2] [1.5] [0.6] [200] [5000]

TABLE 3 Compo- Compo- Compo- Compo- Compo- nent (A) nent (B) nent (D)nent (F) nent (S) Ex. 40 (A)-1  (B)-1 (D)-3 (F)-1 (S)-3 [100] [12.0][3.0] [3.0] [3130] Ex. 41 (A)-4  (B)-1 (D)-3 (F)-1 (S)-3 [100] [12.0][3.0] [3.0] [3130] Ex. 42 (A)-6  (B)-1 (D)-3 (F)-1 (S)-3 [100] [12.0][3.0] [3.0] [3130] Comp. (A)-13 (B)-1 (D)-3 (F)-1 (S)-3 Ex. 5 [100][12.0] [3.0] [3.0] [3130]

TABLE 4 Compo- Compo- nent nent Component Component (A) (B) (D) (E)Component (S) Ex. 43 (A)-15 (B)-1 (D)-1 (E)-1 (S)-1 (S)-2 [100] [38.2][1.5] [0.6] [200] [5000] Ex. 44 (A)-16 (B)-1 (D)-1 (E)-1 (S)-1 (S)-2[100] [38.2] [1.5] [0.6] [200] [5000] Ex. 45 (A)-17 (B)-1 (D)-1 (E)-1(S)-1 (S)-2 [100] [38.2] [1.5] [0.6] [200] [5000] Ex. 46 (A)-18 (B)-1(D)-1 (E)-1 (S)-1 (S)-2 [100] [38.2] [1.5] [0.6] [200] [5000] Ex. 47(A)-19 (B)-1 (D)-1 (E)-1 (S)-1 (S)-2 [100] [38.2] [1.5] [0.6] [200][5000]

In Tables 2 to 4, the values in brackets [ ] indicate the amount (interms of parts by weight) of the component added, and the referencecharacters indicate the following.

(A)-1 to (A)-19: the aforementioned polymeric compounds (1) to (19)

(B)-1: an acid generator consisting of a compound represented bychemical formula (B)-1 shown below

(D)-1: tri-n-octylamine.

(D)-2: a compound represented by chemical formula (D)-2 shown below

(D)-3: a compound represented by chemical formula (D)-3 shown below

(E)-1: salicylic acid

(F)-1: a fluorine-containing polymer (homopolymer) represented byformula (F-1) shown below. Mw: 20,600, Mw/Mn: 1.67. In the chemicalformula (F)-1, the subscript numerals shown on the bottom right of theparentheses ( ) indicate the percentage (mol %) of the respectivestructural units.

(S)-1: γ-butyrolactone

(S)-2: a mixed solvent of PGMEA/PGME/CH (weight ratio: 2250/1500/1250)

(S)-3: a mixed solvent of PGMEA/PGME/CH (weight ratio: 1410/940/780)

PGMEA represents propyleneglycol monomethyletheracetate, PGME representspropyleneglycol monomethylether, and CH represents cyclohexanone.

<Formation of Resist Pattern (1)>

Using a spinner, each resist composition shown in Tables 2 and 4 wasapplied to an 8-inch silicon wafer that had been treated withhexamethyldisilazane (HMDS) at 90° C. for 36 seconds, and the solutionwas then subjected to a bake treatment (PAB) at a bake temperature of100° C. for 60 seconds, thereby forming a resist film (film thickness:60 nm). Subsequently, the resist film was subjected to drawing(exposure) using an electron beam lithography apparatus HL800D (VSB)(manufactured by Hitachi, Ltd.), followed by a bake treatment (PEB: postexposure bake) at a bake temperature of 90° C. for 60 seconds. Then,development was conducted with a 2.38 wt % aqueous TMAH solution(product name: NMD-3; manufactured by Tokyo Ohka Kogyo Co., Ltd.) at 23°C. for 60 seconds.

As a result, in each of the examples, a 1:1 line and space pattern (LSpattern) having a line width of 100 nm and a pitch of 200 nm was formed.

The optimum exposure dose Eop (μC/cm²; sensitivity) with which the LSpattern was formed was determined. The results are shown in Table 5.

[Evaluation of Resolution]

A resist pattern was formed in the same manner as in the above<Formation of resist pattern (1)>, and the critical resolution (nm) withthe above optimum exposure dose Eop was determined using a scanningelectron microscope (product name: S-9380, manufactured by HitachiHigh-Technologies Corporation). The results are indicated under“resolution (nm)” in Table 5.

[Evaluation of Exposure Latitude (EL Margin)]

With respect to the above optimum exposure dose Eop, the exposure dosewith which an LS pattern having a dimension of the target dimension(line width: 100 nm)±10% (i.e., 90 nm to 110 nm) was determined, and theEL margin (unit: %) was determined by the following formula. The resultsare indicated under “EL margin (%)” in Table 5.EL margin(%)=(|E1−E2|/Eop)×100

E1: Exposure dose (μC/cm²) with which an LS pattern having a line widthof 90 nm was formed

E2: Exposure dose (μC/cm²) with which an LS pattern having a line widthof 110 nm was formed

The larger the value of the “EL margin”, the smaller the change in thepattern size by the variation of the exposure dose.

[Evaluation of Line Edge Roughness (LER)]

With respect to the LS pattern formed in the above <Formation of resistpattern (1)> having a line width of 100 nm and a pitch of 200 nm, 3σ wasdetermined as a yardstick for indicating LER. The results are indicatedunder “LER (nm)” in Table 5.

“3σ” indicates a value of 3 times the standard deviation (a) (i.e.,3(s)) (unit: nm) determined by measuring the line width at 400 points inthe lengthwise direction of the line using a scanning electronmicroscope (product name: S-9380, manufactured by HitachiHigh-Technologies Corporation; acceleration voltage: 800V).

The smaller this 3s value is, the lower the level of roughness of theline side walls, indicating that a LS pattern with a uniform width wasobtained.

[Evaluation of Etching Resistance]

With respect to the resist film formed in the above <Formation of resistpattern (1)> prior to drawing (exposure), dry etching (O₂ plasmaetching) was conducted under the following conditions using plasmaobtained from an oxygen gas, and the etching speed was measured. Fromthe difference in the film thickness of the resist film before and afterthe etching, the etching rate (the thickness of the film etched per unittime) was determined. The etching resistance was evaluated with thefollowing criteria. The results are shown in Table 5.

(O₂ Plasma Etching Conditions)

Apparatus: High vacuum RIE apparatus (product name: TCA-2400;manufactured by Tokyo Ohka Kogyo Co., Ltd.).

Gas: a mixed gas containing 60 volume % of an oxygen gas and 40 volume %of a nitrogen gas.

Gas flow rate: 30 sccm (“sccm” refers to a value as measured under 1 atm(atmospheric pressure: 1,013 hPa) at 23° C.)

Temperature inside the chamber: 60° C.

Pressure inside the chamber: 300 mmTorr

Output power applied for generating plasma (RF): 200 W

Treatment time: 60 seconds

(Criteria)

A: Etching rate was 600 nm/min or less

B: Etching rate was over 600 nm/min

TABLE 5 Eop Resolution EL margin LER Etching (μC/cm²) (nm) (%) (nm)resistance Ex. 27 45 60 14.6 7.9 A Ex. 28 51 60 13.5 7.5 A Ex. 29 46 5016.2 7.6 A Ex. 30 44 50 15.5 7.1 A Ex. 31 41 50 14.8 7.4 A Ex. 32 49 5018.4 7.2 A Ex. 33 42 50 17.2 8.1 A Ex. 34 36 50 16.7 7.6 A Ex. 35 40 6014.6 8.1 A Ex. 36 43 60 15.1 7.7 A Ex. 37 46 60 17.0 7.4 A Ex. 38 42 6016.6 7.7 A Ex. 39 46 50 15.9 7.7 A Comp. 59 80 9.2 8.7 A Ex. 3 Comp. 5070 10.7 8.3 B Ex. 4 Ex. 43 35 60 16.2 7.8 A Ex. 44 41 60 16.9 8.0 A Ex.45 45 60 15.5 8.2 A Ex. 46 39 60 17.2 7.7 A Ex. 47 34 60 17.0 7.9 A

From the results shown in Table 5, the resist compositions of theExamples according to the present invention exhibited excellentproperties with respect to sensitivity, resolution, lithographyproperties and etching resistance, as compared to the resistcompositions of the Comparative Examples.

<Formation of Resist Pattern (2)>

An organic anti-reflection film composition (product name: ARC29A,manufactured by Brewer Science Ltd.) was applied to an 12-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 89 nm.

Then, the resist composition was applied to the organic anti-reflectionfilm using a spinner, and was then prebaked (PAB) on a hotplate at 110°C. for 60 seconds and dried, thereby forming a resist film having a filmthickness of 90 nm.

Subsequently, the resist film was selectively irradiated with an ArFexcimer laser (193 nm) through a mask, using an ArF exposure apparatusNSR-5609B (manufactured by Nikon Corporation; NA (numericalaperture)=1.08; Crosspole).

Next, a post exposure bake (PEB) treatment was conducted at a baketemperature of 90° C. for 60 seconds, followed by alkali development for10 seconds at 23° C. in a 2.38% by weight aqueous tetramethylammoniumhydroxide (TMAH) solution. Then, the resist was washed for 15 secondswith pure water, followed by drying by shaking.

As a result, in each of the examples, a 1:1 line and space pattern (LSpattern) having a line width of 49 nm and a pitch of 98 nm was formed.

The optimum exposure dose Eop (mJ/cm²; sensitivity) with which the LSpattern was formed was determined. The results are shown in Table 6.

[Evaluation of Resolution]

A resist pattern was formed in the same manner as in the above<Formation of resist pattern (2)>, and the critical resolution (nm) withthe above optimum exposure dose Eop was determined using a scanningelectron microscope (product name: S-9380, manufactured by HitachiHigh-Technologies Corporation). The results are indicated under“resolution (nm)” in Table 6.

[Evaluation of Exposure Latitude (EL Margin)]

With respect to the above optimum exposure dose Eop, the exposure dosewith which an LS pattern having a dimension of the target dimension(line width: 49 nm)±5% (i.e., 46.55 nm to 51.45 nm) was determined, andthe EL margin (unit: %) was determined by the following formula. Theresults are shown in Table 6.EL margin(%)=(|E1−E2|/Eop)×100

E1: Exposure dose (mJ/cm²) with which an LS pattern having a line widthof 46.55 nm was formed

E2: Exposure dose (mJ/cm²) with which an L/S pattern having a line widthof 51.45 nm was formed

[Evaluation of Line Width Roughness (LWR)]

With respect to each of the LS patterns formed with the above optimumexposure dose Eop and having a space width of 49 nm and a pitch of 98nm, the space width at 400 points in the lengthwise direction of thespace were measured using a measuring scanning electron microscope (SEM)(product name: S-9380, manufactured by Hitachi High-TechnologiesCorporation; acceleration voltage: 300V). From the results, the value of3 times the standard deviation s (i.e., 3s) was determined, and theaverage of the 3s values at 400 points was calculated as a yardstick ofLWR. The results are shown in Table 6.

The smaller this 3s value is, the lower the level of roughness of theline width, indicating that a LS pattern with a uniform width wasobtained.

TABLE 6 Eop Resolution EL margin LWR (mJ/cm²) (nm) (%) (nm) Ex. 40 28 455.4 5.6 Ex. 41 26 42 5.9 5.1 Ex. 42 29 41 5.7 5.1 Comp. 31 48 4.8 6.2Ex. 5

From the results shown in Table 6, the resist compositions of theExamples according to the present invention exhibited excellentproperties with respect to sensitivity, resolution and lithographyproperties, as compared to the resist compositions of the ComparativeExamples.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

The invention claimed is:
 1. A resist composition comprising a basecomponent (A) which exhibits changed solubility in a developing solutionunder action of acid and an acid-generator component (B) which generatesacid upon exposure, the base component (A) comprising a polymericcompound (A1) comprising a structural unit (a1) containing an aciddecomposable group that exhibits increased polarity by the action ofacid and a structural unit (a5) represented by general formula (a5-0)shown below:

wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; R¹ representsa sulfur atom or an oxygen atom; R² represents a single bond or adivalent linking group; and Y represents an aromatic hydrocarbon groupor an aliphatic hydrocarbon group having a polycyclic group, providedthat the aromatic hydrocarbon group or the aliphatic hydrocarbon mayhave a carbon atom or a hydrogen atom thereof substituted with asubstituent.
 2. The resist composition according to claim 1, wherein theamount of the structural unit (a5) based on the combined total of allstructural units constituting the component (A1) is 5 to 70 mol %.
 3. Amethod of forming a resist pattern, comprising: using a resistcomposition according to claim 1 to form a resist film on a substrate,subjecting the resist film to exposure, and subjecting the resist filmto developing to form a resist pattern.
 4. A polymeric compound having astructural unit (a1) containing an acid decomposable group that exhibitsincreased polarity by the action of acid and a structural unit (a5)represented by general formula (a5-0) shown below:

wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; R¹ representsa sulfur atom or an oxygen atom; R² represents a single bond or adivalent linking group; and Y represents an aromatic hydrocarbon groupor an aliphatic hydrocarbon group having a polycyclic group, providedthat the aromatic hydrocarbon group or the aliphatic hydrocarbon mayhave a carbon atom or a hydrogen atom thereof substituted with asubstituent.
 5. The polymeric compound according to claim 4, wherein theamount of the structural unit (a5) based on the combined total of allstructural units constituting the polymeric compound is 5 to 70 mol %.